Amongst all the trigonometric formulas, the most important ones are the right triangle formulas. The Cos θ = Adjacent / Hypotenuse
Cos angle formula
There are many formulas in trigonometry but there are few most important basic formulas in trigonometry when it comes to a right-angle triangle. The Cos theta or 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:
\(\begin{array}{l}Cos \Theta = \frac{Adjacent}{Hypotenuse}\end{array} \) |
Cos Theta Formula 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 =
= 3/5
Example 2: If Sec x = 4/7, find the Cos x?
Solution: As cos x = 1/sec x
Therefore, cos x = 1/ 4/7
= 7/4
Practice questions
Q1) Find cos x, if sin x =2/5?
Q2) Find Cos a, if Sin a = 3/7?
To learn more about Cos theta and other Trigonometric functions, visit BYJU’S.
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