tunjukkan bahwa. a. cos 90° cos 30° + sin 90° sin 30° = cos 60°, b= 1-2 sin^2 45° =0

A. cos 90' . cos30' + sin 90'. sin 30' = cos (90 - 30)' = cos 60' = 1/2
B. 1-2 . sin^2 45' = 0
    1-2 (sin45' . sin45')=0
    1-2 (1/2 akr2 . 1/2 akr2)=0
    1-2 (2/4)=0
   
hasil:
             1-2 . 1/2 = 0
             1-1=0