Question

Prove that 4(cos 66° + sin 84°) = √3 + √15.

Answer 1

Answer:

√3 + √15

Step-by-step explanation:

Formula used:

1.cosC + cosD

= 2 cos((C+D)/2) cos((C-D)/2)

2. cos(36°) = √5 +1)/4

4(cos 66° + sin 84°)

=4(cos 66° + cos 6°)

= 4 × 2 cos((66°+6°)/2) cos((66°-6°)/2)

= 8 cos(36°) cos(30°)

= 8 × (√5 +1)/4 × (√3/2)

= (√5 +1) × (√3)

= √3 + √15.

I hope this answer helps you

Answer 2

Answer:

Step-by-step explanation:

Please refer to the attachment provided below.