Question

Prove that cos130°+cos110°+cos10°=0​

Answer 1

I hope this will help you!

Answer 2

Use the formula cosC+cosD:2cos(C+D/2)cos(C-D/2) Use this in the question: 2cos(10+110/2)cos(10-110/2)+cos130=0 2cos60°cos(-50°)+cos130°=0 2×1/2.cos50+cos130=0 cos50+cos130=0 2cos(50+130/2)cos(50-130/2)=0 2cos90.cos40=0 2×0.cos40=0 0=0 H.P

Explanation: