Cos Theta Formula

Amongst all the trigonometric formulas, the most important ones are the right triangle formulas. The Cos Θ = Adjacent / Hypotenuse

Cos angle formula / Cos phi formula

There are many formulas in trigonometry but there are few most important basic formulas in trigonometry when it comes to right angle triangle. The Cos Θ is the ratio of the adjacent side to the hypotenuse, where (Θ is one of the acute angles. The cosine formula is as follows:

\(Cos \Theta = \frac{Adjacent}{Hypotenuse}\)

Cos theta formula

Cos x Questions

Example 1:

If Sin x = 4/5, Find the value of Cos x?

Solution: Using Trigonometric identities: Cos2x = 1- Sin2x

Cos2x = 1 – (4/5)2

= 1 – 16/25

= (25 – 16) / 25

= 9/25

Cos x = \(\sqrt{9/25}\)

= 3/5

Example 2: If Sec x = 4/7, find the Cos x?

Solution: As Cosec x = 1/sin x

= 1/ 4/7

= 7/4

Practice questions on cos formula trigonometry

Q1) Find cos x, if sin x =25

Q2) Find Cos a, If Sin a = 37

To learn more about Cos theta and other Trigonometric functions, visit BYJU’S.

Practise This Question

In the following questions two Statement - 1 (Assertion) and Statement - 2 (Reason) are provided. Each question has 4 choices (a), (b), (c) and (d) for its answer, out of which ONLY ONE is correct. Mark your responses from the following options:

Statement - 1 : Electromagnetic radiation will be emitted for the transition 2Pz2px.

Statement - 2 : No transition of electron takes place between 2Pz and 2Px orbitals.