since a is in QIII,
sina = -4/5
cosa = -3/5
You sure that's not cos b = 24/25? cot < 0 in QIV. If so, then we have a 7-24-25 triangle.
sinb = 7/25
cosb = 24/25
now just use your difference formula:
cos(a-b) = cosa cosb + sina sinb
Use the given information to evaluate cos (a-b).
Cot a = 3/4, cot b = 24/25; pi<a<3pi/2, 3pi/2<b<2pi.
1 answer
1 answer