In a Triangle ABC if sinA *sinB *sinC +cosA *cosB *cosC =1 . Then find sin C. Share with your friends Share 3 Rahul Raj answered this dear student sin A sin B sin C is clearly less than or equal to sin A sin B. So, the L.H.S. ≤sin A sin B + cos A cos B =cos(A-B). But L.H.S. = 1 i.e. maximum value for a cos . Thus, cos(A-B) ≥ 1. So, cos(A - B) = 1, establishing that A = B for the triangle. Also , for the inequality to turn into an equality , sin C = 1 clearly. So, this is a right-angled triangle right angled at C(=90 degrees.) regards 4 View Full Answer