Proof: cos(a+b) = (cos a)(cos b)-(sin a)(sin b)
Video Lesson (Trigonometry)
Video Tutorial: Proof: cos(a+b) = (cos a)(cos b)-(sin a)(sin b)
This free Trigonometry video tutorial provides a proof of the trig identity: cos(a+b) = (cos a)(cos b)-(sin a)(sin b)