if a+b+c=180 then find cosb+cosc-cosa=4sina/2 cosb/2 cosc/2
Answers
Answered by
1
A) cosA+cosB+cosC=2cos(2A+B)cos(2A−B)+cos(π−(A+B))=2cos(2A+B)cos(2A−B)−cos(A+B)=2cos(2A+B)cos(2A−B)−2cos2(2A+B)+1=2cos(2A+B)(cos(2A−B)−cos(2A+B))+1=2cos(2π−2c)(2sin2Asin2B
Similar questions