Question

show that cos 100 cos 40 + sin 100 sin 40 = $\frac{1}{2}$


if you answer correctly then i will mark you brainliest

Answer 1

Answer:

cos100  cos40   + sin100 sin40

This is in the form of cosA cosB +sinA sinB=cos(A-B)

therefore cos100 cos40 + sin100 sin40= cos(100-40)

cos 100 cos40+ sin100 sin40= cos60

cos100 cos 40+sin 100 sin 40= 1/2  (cos60=1/2 )

hence proved