Question

计算sin105°·cos75°的值等于？

帮我算一下

Answer 1

sin105°cos75°
=sin75°cos75°
=1/2sin(75°x2)
=1/2 sin150°
=1/2 sin30°
=1/4 注：互补角的正弦值相等：sinx=sin(180-x)

Answer 2

sin105°cos75° =sin75°cos75° =1/2sin(75°x2) =1/2 sin150° =1/2 sin30° =1/4