Find the exact value of each expression.

1. sin 50° cos 40° + sin 40° cos 50°

2. (tan pi/3 + tan pi/6) / (1 - tan pi/3 tan pi/6)

In evaluating the following expression in 1, we can use a calculator shifted to degrees mode and applying trigonometric identities

sin 50° cos 40° + sin 40° cos 50° = sin (40+50) = sin 90 = 1

2. (tan pi/3 + tan pi/6) / (1 - tan pi/3 tan pi/6) = tan (pi/3-pi/6) = tan pi/6 = 0.5774