How do you evaluate #cos(pi/3 - pi/6)#?
1 Answer
Jun 3, 2016
If we momentarily forgot how to subtract fractions, we could use the cosine subtraction formula:
#cos(A-B)=cos(A)cos(B)+sin(A)sin(B)#
So, we see that
#cos(pi/3-pi/6)=cos(pi/3)cos(pi/6)+sin(pi/3)sin(pi/6)#
#=1/2(sqrt3/2)+sqrt3/2(1/2)#
#=sqrt3/4+sqrt3/4#
#=(2sqrt3)/4#
#=sqrt3/2#
