Cosec Theta

The cosecant function ‘or’ Cosec Theta is one of the trigonometric functions apart from sine, cosine, tangent, secant, and cotangent. In right-angled trigonometry, the cosecant function is defined as the ratio of the hypotenuse and opposite side.

The mathematical denotation of the sine function is,

\(coses(\theta) = \frac{\text{Hypotenuse Side}}{\text{Opposite Side}}\)

More About Cosec Theta

The derivative of \(cosec(\theta)\) in calculus is \(-cot(\theta)cosec(\theta)\), and the integral of it is \(\ln|cosec(\theta) – cot(\theta)|\). The reciprocal of \(cosec(\theta)\) is \(sin(\theta)\).

Graph of the cosec theta function
Graph of the cosec theta function

Below is a table of cosecant theta values for different degrees and radians.

RadiansDegreeCosecant Value

Important Cosec Theta Formula

Some important properties of the cosecant function and cosec theta formula are:

  • \(cosec(-x) = -cosec(x)\)
  • \(cosec(90°-x) = sec(x)\)
  • \(cosec(x + 2 \pi) = cosec(x)\)
  • \(cosec(\pi – x) = cosec(x)\)
  • \(cosec^2(x) = 1+ cot^2(x)\)

Solved Examples

Question 1. If \(cos(x) = \frac{3}{5}\), calculate the value of \(cosec(x)\).

Solution. Using trigonometric identity, 

\(sin^2(x) = 1 – cos^2(x) = 1 – \frac{9}{25} \frac{16}{25}\)

\(sin(x) = \frac{4}{5}\)

As we know, \(cosec(x) = \frac{1}{sin(x)}\)

\(∴ cosec(x) = \frac{5}{4}\)

Question 2. If \(cot(x) = \frac{4}{5}\), calculate the value of \(cosec(x)\).

Solution. Using trigonometric identity, 

\(cosec^2(x) = 1 + cot^2(x) = (\frac{4}{5})^2 + 1 = \frac{41}{25}\)

\(∴ cosec(x)= \frac{\sqrt{41}}{5}\)


Explain how cosec(-x) = -cosec(x).

As we know, the angle (-x) lies in the 4th quadrant of a graph, and the cosecant is negative in this quadrant. Hence, this shows that cosec(-x) = -cosec(x).

What is cosec theta equal to?

Cosec theta of a right-angled triangle is equal to the ratio of the length of the hypotenuse to the length of the opposite side.

In which quadrants is the cosecant function positive and in which quadrants is it negative?

It can be observed from the above graph that cosec(x) is positive in the 1st and 2nd quadrants and negative in the 3rd and 4th quadrants.

Know More Trigonometric Function

Sin ThetaCos Theta
Tan ThetaSec Theta
Cot Theta
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