若sin(6分之π-角二法)=a,则cos(3分之2π-角二法)=?

2025-04-24 21:40:29
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回答1:

sin(π/6-α)=a
cos(2π/3-α)=-cos(π-2π/3+α)=-cos(π/3+α)=-cos(π/2-(π/6-α))=-sin(π/6-α)=-a