Question

cos 65 degree into cos 25 - sin 65 into sin 25

Answer 1

hey, check it please

Answer 2

sin 25° cos 65° + cos 25° sin 65°

= sin 25° cos (90° – 25°) + cos 25° sin (90° – 25°)

= sin 25° sin 25° + cos 25° + cos 25°

= sin2 25° + cos2 25° = 1.

[∴ cos2 θ + sin2 θ = 1]