Question

The expression sin 50 cos 40 + cos 50 sin 40 is equivalent to

Answer 1

sin (a+b) = sin a. cos b + cos a. sin b

a= 50° and b=40°, then

sin(50+40) = sin 50° . cos 40° + cos 50° . sin 40°

sin(50+40) = sin 90° = 1 and

sin 50° . cos 40° + cos 50° . sin 40° = 1