已知sina=4⼀5,a属于(π⼀2,π),则sin(a+π⼀4)=

2025-12-18 01:33:54
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回答1:

sina=4/5,a属于(π/2,π),所以可得:
cosa=-√(1-sin^2a)=-3/5
sin(a+π/4)
=sinacosπ/4+cosasinπ/4
=4√2/10-3√2/10
=√2/10