In `alpha ge 0 ,betage0 and alpha+betalepi`, then
i) `cos(alpha+beta) = cos alpha cosbeta-sinalpha sinbeta`

In alpha ge 0 ,betage0 and alpha+betalepi , then ii) cos(alpha-beta) = cos alpha cosbeta+sinalpha sinbeta

(i) sin (alpha + beta) = sin alpha cos beta + cos alpha sin beta) (ii) sin (alpha-beta)= sin alpha cos beta- cos alpha sin beta Proof

sin alpha=sinbeta, cos alpha=cos beta then

cos^(2)(alpha+beta)+cos^(2)(alpha-beta)-cos2alpha cos2beta=

If sin alpha = sin beta and cos alpha = cos beta then

If cos alpha + cos beta =0 = sin alpha + sin beta " then " cos (alpha - beta )=

[(cos alpha-cos beta)+i(sin alpha-sinbeta)]^n+[(cos alpha-cos beta)-i(sin alpha-sin beta)]^n=

Evaluate {:[( cos alpha cos beta , cos alpha sin beta , -sin alpha ),( -sin beta , cos beta, 0),( sin alpha cos beta, sin alpha sin beta, cos alpha ) ]:} =0

If alpha, beta are complementary angles, sin alpha = (3)/(5) then cos alpha cos beta-sin alpha sin beta =