化简sin(-a-7兀).cos(a-3兀/2)=

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化简sin(-a-7兀).cos(a-3兀/2)=化简sin(-a-7兀).cos(a-3兀/2)=化简sin(-a-7兀).cos(a-3兀/2)=-sin²α解sin(-a-7兀).co

化简sin(-a-7兀).cos(a-3兀/2)=
化简sin(-a-7兀).cos(a-3兀/2)=

化简sin(-a-7兀).cos(a-3兀/2)=
-sin²α

解sin(-a-7兀).cos(a-3兀/2)
=-sin(a+7兀).cos(3兀/2-a)
=-sin(a+兀).cos(3兀/2-a)
=sina×(-sina)
=-sin^2a