Half angle identities?

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

1 Answer
Jul 24, 2018

As below.


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.


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)#