解:
cos(x+π/4)+sin(x+π/4)
=√2[√2/2 cos(x+π/4)+√2/2 sin(x+π/4)]
=√2[cosπ/4 cos(x+π/4)+sinπ/4 sin(x+π/4)]
=√2 cos(x+π/4-π/4)
=√2cosx
希望可以帮到你
祝学习快乐
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