Question

if A and B are measures of an acute angle ,tan a = 1 /root3 and sin b =1 /2 then cos( a + b )=

Answer 1

tan a = 1/√3
a = 30°

sin b = 1/2
b = 30°

a+b = 30 + 30 = 60°
cos (a+b) = cos 60° = 1/2