Please help?
1 Answer
Feb 28, 2018
Explanation:
The key is to apply the sum/difference identities
#1. sin(a+b)=sin(a)cos(b)+sin(b)cos(a)#
#2. cos(a-b)=cos(a)cos(b)+sin(a)sin(b)#
#3. tan(a-b)=(tan(a)-tan(b))/(1+tan(a)tan(b))#
We know
By the pythagorean trigonometric identity
notice how the sign behaves depending on the quadrant
#sin(a)=sqrt(1-(12/13)^2)=5/13#
#cos(b)=-sqrt(1-(8/17)^2)=-15/17#
First exercise
The two remaining are left for you, as it follow the same method