these are just applications of the addition formulas:
tan(A+B) = (tanA+tanB)/(1 - tanA tanB)
cos(A-B) = cosA cosB + sinA sinB
sin(A-B) = sinA cosB - cosA sinB
Evaluate each expression:
a) ( tan π/12 + tan 7π/4 ) / ( 1 - tan π/12 x tan 7π/4)
b) cos π/4 cos π/12 + sin π/4 x sin π/12
c) sin 7π/5 cos π/15 - cos 7π/5 sin π/15
1 answer