Tan 90 Degrees

In Trigonometry, Sine, Cosine and Tangent are the three primary ratios, based on which the whole trigonometric functions and formulas are designed. Each trigonometric functions have their equivalent importance. Basically, these ratios are used to find the angles and the sides or length of sides of a right-angles triangle. These angles are calculated with respect to sin, cos and tan functions. Usually, the degrees are considered as 00, 300, 450, 600, 900, 1800, 2700 and 3600. In this article, we will discuss, how to find the value for tan 90 degrees along with other degrees or radians.

Tan 90 Degrees Value

As discussed, when we speak about trigonometry, Sine, Cosine and Tangent are the principle trigonometric functions. Let us give a brief about all three functions or ratios with respect to a right-angled triangle.

Sine functions denote that for a given right-angled triangle, the sin of angle\(\theta\) is equal to the ratio of the opposite side to the angle and hypotenuse.

Sin \(\theta\)=Opposite Side/Hypotenuse

Cosine function denotes that for a given right-angled triangle, the cos of angle\(\theta\) is equal to the ratio of the adjacent side to the angle and hypotenuse.

Cos \(\theta\)=Adjacent Side/Hypotenuse

Tangent function denotes that for a given right-angled triangle, the tan of angle\(\theta\) is equal to the ratio of the opposite side to the angle and adjacent side or base.

Tan \(\theta\)=Opposite Side/Adjacent Side


We can also represent the tangent function as the ratio of the sine function and cosine function.

∴ Tan\(\theta\)=Sin \(\theta\)/Cos \(\theta\)

So, tan 90 degrees in fraction we can write as,

Tan 900=Sin 900 / Cos900

From the trigonometric table, we know,

Sin 900=1


∴ Tan 900=1/0=∞

That means, we cannot define Tan 900 value.

For a unit circle, which has a radius as 1, we can derive the tangent values of all the degrees. With the help of a unit circle drawn on the XY plane, we can find out all the trigonometric ratios and values. As you can see on the graph, Tan 90 degrees unit circle value is undefined or infinite.

In the same, we can derive other values of tangent degrees(00,300,450,600,900,1800,2700 and 3600). Below is the trigonometry table, which defines all the values of tangent along with other trigonometric ratios.

Angle 00 300 450 600 900 1800 2700 3600
Sin 0 1/2 \(1/\sqrt{2}\) \(\sqrt{3}/2\) 1 0 -1 0
Cos 1 \(\sqrt{3}/2\) \(1/\sqrt{2}\) 1/2 0 -1 0 1
Tan 0 1/\(\sqrt{3}\) 1 \(\sqrt{3}\) 0 0
Cot \(\sqrt{3}\) 1 1/\(\sqrt{3}\) 0 0
Sec 1 2/\(\sqrt{3}\) \(\sqrt{2}\) 2 -1 1
Cosec 2 \(\sqrt{2}\) 2/\(\sqrt{3}\) 1 -1

Trigonometry Equations Based on Tangent Function

Tangent functions are used to formulate multiple trigonometric formulas.

The basic formula for tangent function is;

Tan\(\Theta\)=Perpendicular/ Base





Other formulas:

  1. Tan(-\(\Theta\))=-Tan\(\Theta\)
  2. Tan (x+y)= \(\frac{tan x +tan y}{1-tan x tan y}\)
  3. Tan (x-y)=\(\frac{tan x -tan y}{1+tan x tan y}\)
  4. Tan 2x=2 tan x/1-tan2 x
  5. Tan 3x= 3tan x-tan3 x/1-3 tan2 x
  6. Tan (90-\(\Theta\))=Cot\(\Theta\)
  7. Tan (90+\(\Theta\))= -Cot\(\Theta\)

Example:Find the value of tan(90-45)0

Answer: We know, tan(90-\(\Theta\))=cot\(\Theta\)

∴ tan(90-45)=cot 450

And cot 450 =1

So, tan(90-45)0=1

Example: Show that tan 3x.tan 2x.tanx= tan 3x-tan 2x-tan x

Answer: We can write, 3x=2x+x

Alos, tan 3x= tan (2x+x)

By the formula,tan (x+y)= \(\frac{tan x +tan y}{1-tan x tan y}\)

We can write,

tan 3x=tan (2x+x)= \(\frac{tan 2x +tan y}{1-tan 2x tan y}\)

tan 3x-tan 2x- tan x=tan 3x.tan 2x.tan x

Or tan 3x.tan 2x.tan x=tan 3x-tan 2x- tan x

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Practise This Question

Match the following:

Given sin x = 25 and x ϵ (0,Π2)

(p) cos x(1)52(q) tan x(2)212(r) cosec x(3)215(4)221

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