Question

cos 25 degree cos 20 degree + sin 25 degree sin 20 degree

Answer 1

sin90-25 sin90-20 +cos 90-25 cos 90-20

sin65 sin 70 +cos65 cos 70

=1

Answer 2

hey mate ur ans

cos 25 degree cos 20 degree + sin 25 degree sin 20 degree

using
cos(s)cos(t)+ sin(s)sin(t)=cos(s-t)

cos (25-20)

cos 5 or 0.283