Question 816603
Solve for B; cos(3B - pi/4) =1/2
assume(3B-π/4) is an acute angle
cos(3B-π/4)=1/2=cos(π/3)
3B-π/4=π/3
3B=π/3+π/4=4π/12+3π/12=7π/12
3B=7π/12
B=7π/36