PDA

View Full Version : How would I prove cos(x-y)/cosxcosy=1+tanxtany

aamm
Jan 23, 2008, 08:30 PM
how would I prove cos(x-y)/cosxcosy=1+tanxtany
jiten55
Jan 24, 2008, 01:16 AM
cos(x-y) = cosx cosy + sinx siny

divide both sides by cosx cosy

(remember: sinA/cosA = tan A)