cos(A+B)=cosA+cosB成立时,A、B可能的值
问题描述：
cos(A+B)=cosA+cosB成立时,A、B可能的值
答
试着推几步：cos(A+B)= cosA+cosBcos(A+B)= 2cos[(A+B)/2]*cos[(A-B)/2][cos(A+B)]^2= (2*{cos[(A+B)/2]}^2)* (2*{cos[(A-B)/2]}^2)[cos(A+B)]^2= [cos(A+B)+1]*[cos(A-B)+1]cos(A-B)+1 = [cos(A+B)]^2/[cos(A+B)+1]...