Question

Find the value of cos 100° cos 40° + sin 100° sin 40° = ?​

Answer 1

Answer:

0.5

Step-by-step explanation:

CosACosB + SinASinB = Cos(A-B)

Cos100Cos40 + Sin100Sin40 = Cos(100-40)°

                                                 = Cos 60°

                                                 = $\frac{1}{2}$

                                                 =0.5

Answer 2

Answer:

cos (90°-100)cos (45°-40)+sin(90°-100)sin (45°-40)=

cos-10°cos5°+sin-10°sin5°=

cos-15°+sin-15°=

cos15\sin-15°=

cos sin=0