∵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?

因为sinx-cosx
=√2(√2/2*sinx-√2/2cosx)
=√2(sinxcosπ/4-cosxsinπ/4)
=√2sin(x-π/4)