Question

为什么sin²(兀/4)等于cos²(兀/4)

为什么sin²(x+π/4)-cos²(x+π/4)] =2sin²(x+π/4)-1
就你之前解答的那道三角函数题.

Answer 1

sin²(x+π/4)-cos²(x+π/4)] =2sin²(x+π/4)-1
因为cos²(x+π/4)] =1-sin²(x+π/4)
所以sin²(x+π/4)-cos²(x+π/4)] =2sin²(x+π/4)-1