If sum_(i=1)^(n) cos(A_i) = nni=1cos(Ai)=n then find sum_(i=1)^(n) sin(A_i)ni=1sin(Ai)?

1 Answer
Jul 2, 2018

0 (assuming all the A_iAis are real)

Explanation:

Since the maximum value of cos(A)_icos(A)i for real A_iAi is 1, the sum of nn such numbers can be nn if and only if each one of them is equal to 1. Thus

cos(A_i) = 1,qquad i=1,2,...,n implies

sin(A_i) = sqrt(1-cos^2(A_i))=0,qquad i=1,2,...,n

Thus, the required sum is 0.