trigonometri

sin95.sin55−cos40/2=?

(sin95.sin55−cos40)/2 mi
sin95.sin55−(cos40)/2 mi?

sinx . siny = -1/2[ cos(x+y) + cos(x-y) ]

sin95.sin55 = -1/2[ cos150 + cos40]

-cos150/2 + cos40/2 - cos40/2
-cos150/2
cos30/2
√3/4