Question

cos(A+B)=cosA+cosB成立时,A、B可能的值

Answer 1

试着推几步：

cos(A+B)= cosA+cosB

cos(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]

以上是A+B与A-B应该满足的函数关系~