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What Is the Value Of Cot 90 Degrees

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How to Find the Value Of Cot 90 Using Sin and Cos Formula

The value of cot 90 (in degrees) is equivalent to 0 in trigonometry. Trigonometry ratios of complementary angles can be used to generate related formulae based on this value. Many arithmetic issues are solved using the trigonometric ratios table of sin, cos, tan, cosec, sec, and cot for normal angles from 0° to 360°. In trigonometry, we may use several formulae to get the needed values for trigonometric functions. In this post, you will learn what the cot 90 value is and how to calculate the value of cot 90° through derivation.


Cot 90 Value

The Cot 90 value (in degrees) is:


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What are Cot 90 Degrees in Radians?

Cot 90° may be represented as cot π/2 in a circular system. The cot may be represented as cos over sin, as we all know. The unit circle may be used to derive the cot 90 value using this relationship.


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The tangent values of all the degrees may be calculated for a unit circle with a radius of one. We may determine all the trigonometric ratios and values with the assistance of a unit circle drawn on the XY plane.


In the above circle,


cos 90° = 0 and

sin 90° = 1


Now,


cot 90° = cos 90°/sin 90° = 0/1 = 0


Hence, the value of Cot 90 degrees is zero.


Cot 90 Step by Step Derivation

As we all know the value of cot 90 degrees is always zero. Let’s take an overlook how it is calculated,


Recall that cot(θ) = \[\frac{1}{tan(θ)} \]


and the tan(θ) = \[ \frac{sin(θ)}{cos(θ)} \]


Now, we know that,


cot(θ) = \[ \frac{1}{tan(θ)} = \frac{1}{\frac{sin(θ)}{cos(θ)}} = \frac{cos(θ)}{sin(θ)} \]


Now, an instance of θ put 90 degrees,


\[ cot (θ) = \frac{cos(θ)}{sin(θ)} \]


\[ cot (90) = \frac{cos(90)}{sin(90)} \]


By using, the unit circle (below) that,


sin 90° = 1


cos 90° = 0


cot(90) = \[ \frac{0}{1} \]


cot(90) = 0


Hence its proved.


Cot 90 Minus Theta

Let us obtain the formula for cot 90 – theta,


i.e. cot(90° – θ).


cot(90° – θ) = cot(1 × (90° – θ))


Here, 90 degrees is multiplied by an odd number 1. As a result, the trigonometric function will change to its reciprocal form. That indicates we should write "tan" in the following step.


Also, (90° – θ) is in the first quadrant, with a positive tan (all the six functions are positive in this quadrant).


cot(90° – θ) = tan θ


Put θ = y


Then we get,


cot(90° – y) = tan y


And


Again put θ = c


Then we get,


cot(90° – c) = tan c


All of these formulae can be expressed as follows:


cot(π/2 – θ) = tan θ


cot(π/2 – y) = tan y


cot(π/2 – c) = tan c


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Cot 90 Plus Theta

Let us obtain the formula for cot 90 + theta,


i.e. cot(90° + θ).


cot(90° + θ) = cot(1 × (90° + θ))


In this case, 90 degrees is multiplied by an odd number of one. As a result, the trigonometric function will revert to its reciprocal form. That indicates we should write "tan" in the following step.


Also, 90° + θ is located in the second quadrant, where the tan is negative (only sine and cosecant are positive in this quadrant).


Now, cot(90° + θ) = -tan θ


Put θ = y,


Then we get,


cot(90° + y) = -tan y


And,


Put θ = c


cot(90° + c) = -tan c


All of these formulae can be expressed as follows:


cot(π/2 + θ) = -tan θ


cot(π/2 + y) = -tan y


cot(π/2 + c) = -tan c


Where is Cot Undefined

For some particular angles, the value of the cot is undefined. The table of trigonometric ratios below can help you understand how cot is undefined.

Trigonometry Ratios

Angles (In Degrees)

\[0^{\circ} \]

\[30^{\circ} \]

\[45^{\circ} \]

\[60^{\circ} \]

\[90^{\circ} \]

\[1800^{\circ} \]

\[270^{\circ} \]

\[360^{\circ} \]

Angles (In Radians)

\[0^{\circ} \]

\[\frac{\pi}{6}\]

\[\frac{\pi}{4}\]

\[\frac{\pi}{3}\]

\[\frac{\pi}{2}\]

\[\pi\]

\[\frac{3\pi}{2}\]

2\[\pi\]

sin θ

0

\[ \frac{1}{2}\]

\[ \frac{1}{\sqrt{2}}\]

\[ \frac{\sqrt{3}}{2}\]

1

0

-1

0

cos θ

1

\[ \frac{\sqrt{3}}{2}\]

\[ \frac{1}{\sqrt{2}}\]

\[ \frac{1}{2}\]

0

-1

0

1

tan θ

0

\[ \frac{1}{\sqrt{3}}\]

1

\[\sqrt{3}\]

\[\infty\]

0

\[\infty\]

0

cosec θ

\[\infty\]

2

\[\sqrt{2}\]

\[\frac{2}{\sqrt{3}} \]

1

\[\infty\]

-1

\[\infty\]

sec θ

1

\[\frac{2}{\sqrt{3}} \]

\[\sqrt{2}\]

2

\[\infty\]

-1

\[\infty\]

1

cot θ

\[\infty\]

\[\sqrt{3}\]

1

\[\frac{1}{\sqrt{3}} \]

0

\[\infty\]

0

\[\infty\]


Thus, the cot value is undefined (Unknown) for 0°, 180° and 360°. Since the ratio of cos and sin at these angles equals 1/0, these values are represented as undefined or infinite (\[\infty\]).


The value of cot 90 (in degrees) is equivalent to 0 in trigonometry. Many arithmetic issues are solved using the trigonometric Table of sin, cos, tan, cosec, sec, and cot for normal angles from 0° to 360°. This article is more helpful for any student who is confused about the cot values.

Conclusion:

Cot 90 degrees is the cotangent trigonometric function value for a 90-degree angle. Cot 90° has a value of 0.

No, the value of cot 90 has been defined, and it is 0.

The value of cot 90 plus theta is -tan and can be written as $\cot(90^\circ + \theta)$.

As a result, $\cot(90^\circ + \theta) = - \tan \theta$.

The value of cot 90 minus theta is tan and can be written as $\cot(90^\circ - \theta)$. As a result, $\cot(90^\circ - \theta) = \tan \theta$.

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FAQs on What Is the Value Of Cot 90 Degrees

1. What is the value of cot 90°?

The value of cot 90° is 0. Cotangent is defined as cot θ = cos θ / sin θ. Since at 90°, cos 90° = 0 and sin 90° = 1, we get:

  • cot 90° = 0 / 1 = 0
This is an important standard trigonometric value used in trigonometry tables and identities.

2. How do you find the value of cot 90 degrees?

You find cot 90° using the formula cot θ = cos θ / sin θ. Follow these steps:

  • Step 1: Recall that cos 90° = 0
  • Step 2: Recall that sin 90° = 1
  • Step 3: Substitute into the formula → cot 90° = 0 / 1
  • Step 4: Simplify → cot 90° = 0
This method uses standard trigonometric ratios from the unit circle.

3. Why is cot 90° equal to 0?

Cot 90° equals 0 because the cosine of 90° is zero while the sine is non-zero. Since cot θ = cos θ / sin θ, and at 90°:

  • cos 90° = 0
  • sin 90° = 1
Dividing 0 by 1 gives cot 90° = 0. The value is defined because the denominator is not zero.

4. What is cot 90° in radians?

The value of cot(π/2) is 0. Since 90° = π/2 radians, and cotangent is defined as cot θ = cos θ / sin θ, we evaluate:

  • cos(π/2) = 0
  • sin(π/2) = 1
Therefore, cot(π/2) = 0 / 1 = 0. The value remains the same whether measured in degrees or radians.

5. Is cot 90° defined or undefined?

The value of cot 90° is defined and equal to 0. A trigonometric ratio is undefined only when its denominator is zero. Since cot θ = cos θ / sin θ and sin 90° = 1 (not zero), the expression is valid. Therefore, cot 90° = 0 and is properly defined.

6. What is the formula for cotangent?

The formula for cotangent is cot θ = cos θ / sin θ or equivalently cot θ = 1 / tan θ. It is one of the six basic trigonometric functions. Important related identities include:

  • tan θ = sin θ / cos θ
  • cot θ × tan θ = 1
This formula helps evaluate values like cot 90°.

7. What is the value of cot 90° using tan 90°?

The value of cot 90° is 0 because cotangent is the reciprocal of tangent. Since cot θ = 1 / tan θ and tan 90° is undefined, its reciprocal approaches 0. Alternatively, using the direct formula cot θ = cos θ / sin θ gives:

  • 0 / 1 = 0
Hence, cot 90° = 0.

8. What is the value of cot 90° in the unit circle?

In the unit circle, cot 90° equals 0. At 90°, the coordinate on the unit circle is (0, 1). Since:

  • cos θ = x-coordinate = 0
  • sin θ = y-coordinate = 1
Using cot θ = cos θ / sin θ, we get 0 / 1 = 0. This confirms the standard trigonometric value.

9. What is the difference between cot 90° and tan 90°?

The key difference is that cot 90° = 0 while tan 90° is undefined. This happens because:

  • tan θ = sin θ / cos θ, and cos 90° = 0 → division by zero (undefined)
  • cot θ = cos θ / sin θ, and sin 90° = 1 → valid division
Thus, cotangent is defined at 90°, but tangent is not.

10. What are the common mistakes when finding the value of cot 90°?

A common mistake is confusing cot 90° with tan 90° and assuming both are undefined. Remember:

  • cot 90° = 0
  • tan 90° is undefined
  • Cotangent uses cos θ / sin θ, not the reverse
Always check which function has zero in the denominator to avoid errors in trigonometric calculations.