Half angle identities?

tan pi/12=tan (pi/6)/2

1 Answer
Jul 24, 2018

As below.

Explanation:

Special cases of the sum and difference formulas for sine and cosine yields what is known as the double‐angle identities and the half‐angle identities.

https://www.onlinemathlearning.com/double-angle-formula.html

In addition to the above, sine and cosine can be expressed in terms of tangent also.

#sin 2theta = (2 tan theta) / (1 + tan62 theta)#

#cos 2theta = (sin 2theta) / (tan 2theta) = (1 - tan^2 theta) / (1 + tan ^2 theta)#