∵sinx-cosx≠0 ∴根号2sin(x-π/4)≠0 为什么?
问题描述:
∵sinx-cosx≠0 ∴根号2sin(x-π/4)≠0 为什么?
答
因为sinx-cosx
=√2(√2/2*sinx-√2/2cosx)
=√2(sinxcosπ/4-cosxsinπ/4)
=√2sin(x-π/4)