Question

cos(180-alfa) daca cos de alfa=3/4

Answer 1

cos(a-b)= cos a x cos b + sin a x sin b
cos(180 - $\alpha$) = cos 180 x cos $\alpha$ + sin 180 x sin $\alpha$
=-1 x 3/4 + 0 x sin $\alpha$ = -1 x 3/4 = -3/4