In trigonometry, there are four popular double angle trigonometric identities and they are used as formulae in theorems and in solving the problems. So, let’s learn each double angle identity with mathematical proof.

The sine of double angle is equal to two times the product of sine and cosine of angle.

$\sin{2\theta} \,=\, 2\sin{\theta}\cos{\theta}$

The cosine of double angle is equal to the subtraction of square of sine from square of cosine of angle.

$\cos{2\theta} \,=\, \cos^2{\theta}-\sin^2{\theta}$

$\tan{2\theta} \,=\, \dfrac{2\tan{\theta}}{1-\tan^2{\theta}}$

$\cot{2\theta} \,=\, \dfrac{\cot^2{\theta}-1}{2\cot{\theta}}$

Learn how to use the double angle trigonometric identities as formulae in mathematical problems.

Latest Math Topics

Jan 06, 2023

Jan 03, 2023

Jan 01, 2023

Dec 26, 2022

Dec 08, 2022

Latest Math Problems

Jan 31, 2023

Nov 25, 2022

Nov 02, 2022

Oct 26, 2022

A best free mathematics education website for students, teachers and researchers.

Learn each topic of the mathematics easily with understandable proofs and visual animation graphics.

Learn how to solve the maths problems in different methods with understandable steps.

Copyright © 2012 - 2022 Math Doubts, All Rights Reserved