In the Triangle Below What is the Tangent of 45

In the Triangle Below What is the Tangent of 45


Tangent, written equally tan⁡(θ), is one of the six fundamental trigonometric functions.

Tangent definitions

There are 2 main ways in which trigonometric functions are typically discussed: in terms of right triangles and in terms of the unit circle. The right-angled triangle definition of trigonometric functions is most often how they are introduced, followed past their definitions in terms of the unit of measurement circle.

Correct triangle definition

For a right triangle with i astute bending, θ, the tangent value of this angle is defined to exist the ratio of the opposite side length to the adjacent side length.

The sides of the right triangle are referenced equally follows:

  • Side by side: the side next to θ that is not the hypotenuse
  • Reverse: the side opposite θ.
  • Hypotenuse: the longest side of the triangle opposite the right angle.

The other ii well-nigh unremarkably used trigonometric functions are cosine and sine, and they are divers as follows:

Tangent is related to sine and cosine every bit:


Observe tan(⁡θ) for the right triangle beneath.

Nosotros can also use the tangent function when solving real globe problems involving right triangles.


Jack is continuing 17 meters from the base of operations of a tree. Given that the bending from Jack’s feet to the top of the tree is 49°, what is the peak of the tree, h? If the tree falls towards Jack, will information technology land on him?

Since nosotros know the adjacent side and the angle, we can use

to solve for the height of the tree.

h = 17 × tan⁡(49°) ≈ 19.56

So, the height of the tree is 19.56 grand. If Jack does not move, the tree volition land on him if information technology falls in his management, since xix.56 > 17.

Unit circle definition

Trigonometric functions tin also exist defined with a unit circle. A unit circle is a circle of radius 1 centered at the origin. The correct triangle definition of trigonometric functions allows for angles between 0° and 90° (0 and

in radians). Using the unit circle definitions allows us to extend the domain of trigonometric functions to all real numbers. Refer to the effigy below.

On the unit circle, θ is the angle formed betwixt the initial side of an angle along the x-axis and the last side of the angle formed by rotating the ray either clockwise or counterclockwise. On the unit circumvolve, tan⁡(θ) is the length of the line segment formed past the intersection of the line x=1 and the ray formed by the concluding side of the angle as shown in bluish in the effigy above.

Different the definitions of trigonometric functions based on right triangles, this definition works for any angle, non just acute angles of right triangles, as long as information technology is within the domain of tan⁡(θ), which is undefined at odd multiples of 90° (). Thus, the domain of tan⁡(θ) is θ∈R,
. The range of the tangent function is -∞<y<∞.

Values of the tangent office

At that place are many methods that tin can be used to determine the value for tangent such as referencing a table of tangents, using a calculator, and approximating using the Taylor Series of tangent. In virtually practical cases, it is not necessary to compute a tangent value past hand, and a table, computer, or some other reference will be provided.

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Tangent calculator

The post-obit is a calculator to find out either the tangent value of an angle or the angle from the tangent value.

Commonly used angles

While we can discover tan⁡(θ) for whatsoever bending, in that location are some angles that are more frequently used in trigonometry. Below is a tabular array of tangent values for ordinarily used angles in both radians and degrees.

Angle in degrees Angle in radians Tangent value Tangent value in decimals
15° 0.268
30° 0.577
45° 1 ane
60° 1.732
75° 3.732
90° Undefined Undefined
180° π
270° Undefined Undefined
360° 2π

From these values, tangent can be determined every bit
. Cosine has a value of 0 at ninety° and a value of ane at 0°. On the other manus, sine has a value of one at 90° and 0 at 0°. As a result, tangent is undefined whenever cos⁡(θ)=0, which occurs at odd multiples of 90° (), and is 0 whenever sin⁡(θ)=0, which occurs when θ is an integer multiple of 180° (π). The other usually used angles are 30° (), 45° (), lx° () and their corresponding multiples. The cosine and sine values of these angles are worth memorizing in the context of trigonometry, since they are very commonly used, and can exist used to determine values for tangent. Refer to the cosine and sine pages for their values.

Knowing the values of cosine, sine, and tangent for angles in the first quadrant allows us to make up one’s mind their values for corresponding angles in the residual of the quadrants in the coordinate plane through the apply of reference angles.

Reference angles

A reference angle is an acute angle (<90°) that can be used to represent an angle of any mensurate. Any angle in the coordinate plane has a reference angle that is between 0° and xc°. It is always the smallest bending (with reference to the x-axis) that can be made from the terminal side of an angle. The effigy below shows an angle θ and its reference angle θ’.

Because θ’ is the reference bending of θ, both tan⁡(θ) and tan⁡(θ’) have the aforementioned value. For case, thirty° is the reference angle of 150°, and their tangents both have a magnitude of
, albeit they have different signs, since tangent is positive in quadrant I simply negative in quadrant 2. Because all angles have a reference bending, we really merely demand to know the values of tan⁡(θ) (too as those of other trigonometric functions) in quadrant I. All other corresponding angles volition have values of the aforementioned magnitude, and we but need to pay attention to their signs based on the quadrant that the concluding side of the angle lies in. Beneath is a table showing the signs of cosine, sine, and tangent in each quadrant.

Tangent Sine Cosine
Quadrant I + + +
Quadrant II +
Quadrant 3 +
Quadrant IV +

In one case nosotros make up one’s mind the reference bending, we can determine the value of the trigonometric functions in any of the other quadrants by applying the appropriate sign to their value for the reference bending. The following steps tin be used to find the reference angle of a given angle, θ:

  1. Subtract 360° or 2π from the bending as many times as necessary (the angle needs to be between 0° and 360°, or 0 and 2π). If the resulting bending is betwixt 0° and ninety°, this is the reference angle.
  2. Decide what quadrant the terminal side of the angle lies in (the initial side of the angle is along the positive 10-axis)
  3. Depending what quadrant the terminal side of the bending lies in, use the equations in the table below to find the reference angle. In quadrant I, θ’=θ.
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Quadrant 2 Quadrant III Quadrant IV
θ’= 180° – θ θ’= θ – 180° θ’= 360° – θ


Discover tan⁡(240°).

  1. θ is already betwixt 0° and 360°
  2. 240° lies in quadrant 3
  3. 240° – 180° = 60°, so the reference angle is 60°

tan⁡(60°)=. 240° is in quadrant III where tangent is positive, so: tan⁡(240°)=tan⁡(60°)=


Find tan⁡(690°).

  1. 690° – 360° = 330°
  2. 330° lies in quadrant 4
  3. 360° – 330° = thirty°

tan⁡(30°) =
. 330° is in quadrant 4 where tangent is negative, so:

tan⁡(330°) = -tan⁡(30°) =

Properties of the tangent office

Below are a number of backdrop of the tangent role that may be helpful to know when working with trigonometric functions.

Tangent is a cofunction of cotangent

A cofunction is a function in which f(A) = g(B) given that A and B are complementary angles. In the context of tangent and cotangent,

tan⁡(θ) = cot⁡(90° – θ)

cot⁡(θ) = tan⁡(90° – θ)


tan⁡(30°) = cot⁡(ninety° – xxx°)

tan⁡(thirty°) = cot⁡(threescore°)

Referencing the unit of measurement circle shown in a higher place, the fact that
, and
, we can meet that:

tan⁡(30°) = cot⁡(60°) =

Tangent is an odd office

An odd function is a office in which -f(x)=f(-x). Information technology has symmetry virtually the origin. Thus,

-tan⁡(θ) = tan⁡(-θ)


-tan⁡(30°) = tan⁡(-thirty°)

-tan⁡(thirty°) = tan⁡(330°)

Referencing the unit of measurement circle or a table, we can find that tan⁡(30°)=. tan⁡(-thirty°) is equivalent to tan⁡(330°), which we determine has a value of
. Thus, -tan⁡(xxx°) = tan⁡(330°) =

Tangent is a periodic part

A periodic function is a function, f, in which some positive value, p, exists such that

f(x+p) = f(x)

for all x in the domain of f, p is the smallest positive number for which f is periodic, and is referred to as the menstruum of f. The flow of the tangent function is π, and it has vertical asymptotes at odd multiples of
. Nosotros tin write this as:

tan⁡(θ+π) = tan⁡(θ)

To business relationship for multiple full rotations, this can also be written as

tan⁡(θ+nπ) = tan⁡(θ)

where north is an integer.

Unlike sine and cosine, which are continuous functions, each period of tangent is separated by vertical asymptotes.


tan⁡(405°) = tan(45° + two×180°) = tan(45°) = 1

Graph of the tangent part

The graph of tangent is periodic, meaning that it repeats itself indefinitely. Unlike sine and cosine however, tangent has asymptotes separating each of its periods. The domain of the tangent function is all real numbers except whenever cos⁡(θ)=0, where the tangent part is undefined. This occurs whenever
. This can exist written as θ∈R,
. Below is a graph of y=tan⁡(ten) showing 3 periods of tangent.

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In this graph, we can meet that y=tan⁡(ten) exhibits symmetry near the origin. Reflecting the graph across the origin produces the same graph. This confirms that tangent is an odd role, since -tan⁡(x)=tan(-x).

Full general tangent equation

The full general class of the tangent function is

y = A·tan(B(10 – C)) + D

where A, B, C, and D are constants. To exist able to graph a tangent equation in general course, we demand to first sympathize how each of the constants affects the original graph of y=tan⁡(x), as shown to a higher place. To apply annihilation written below, the equation must be in the form specified above; be careful with signs.

A—the amplitude of the office; typically, this is measured every bit the elevation from the center of the graph to a maximum or minimum, as in sin⁡(x) or cos⁡(x). Since y=tan⁡(x) has a range of (-∞,∞) and has no maxima or minima, rather than increasing the top of the maxima or minima, A stretches the graph of y=tan⁡(ten); a larger A makes the graph arroyo its asymptotes more quickly, while a smaller A (<1) makes the graph approach its asymptotes more slowly. This is sometimes referred to as how steep or shallow the graph is, respectively.

Compared to y=tan⁡(x), shown in regal below, the office y=5tan⁡(x) (red) approaches its asymptotes more than steeply.

B—used to determine the period of the function; the period of a function is the altitude from superlative to peak (or any indicate on the graph to the side by side matching bespeak) and can be found equally
. In y=tan⁡(x) the period is π. We tin confirm this by looking at the tangent graph. Referencing the figure above, we can see that each menses of tangent is bounded by vertical asymptotes, and each vertical asymptote is separated past an interval of π, so the period of the tangent function is π.

Compared to y=tan⁡(x), shown in purple below, which has a menstruation of π, y=tan⁡(2x) (red) has a menses of
. This means that the graph repeats itself every

rather than every π.

C—the phase shift of the function; stage shift determines how the function is shifted horizontally. If C is negative, the function shifts to the left. If C is positive the role shifts to the right. Exist wary of the sign; if we have the equation

and then C is

, considering this equation in standard grade is
. Thus, we would shift the graph

units to the left.

The figure below shows y=tan⁡(ten) (purple) and

(red). Using the zero of y=tan⁡(x) at (0, 0) as a reference, we can encounter that the same zero in

has been shifted to (, 0).

D—the vertical shift of the function; if D is positive, the graph shifts upward D units, and if it is negative, the graph shifts downward.

Compared to y=tan⁡(ten), shown in purple beneath, which is centered at the x-centrality (y=0), y=tan⁡(x)+2 (red) is centered at the line y=2 (blueish).

Putting together all the examples in a higher place, the effigy below shows the graph of

(red) compared to that of y=tan⁡(10) (majestic).

Run into as well
sine, cosine, unit circle, trigonometric functions, trigonometry.

In the Triangle Below What is the Tangent of 45