Question

Show that cos 100° cos 40° + sin 100° sin 40º =1/2.​

Answer 1

Answer:

A=100° & B=40°

cos 100°.cos 40° + sin 100° .sin 40°

=cos(100°-40°)

=cos(60°)

and value of cos(60°)=1/2=0.5

Hence

Cos100°.cos40°+sin100°.sin40° = 1/2