A为锐角,f(A)=[cos(π-2A)-1]sin(π+A/2)sin(π/2-A/2)/sin^2(π/2-A/2)-sin^2(π-A/2)
人气:422 ℃ 时间:2020-04-14 15:55:04
解答
f(A)=[cos(π-2A)-1]sin(π+A/2)sin(π/2-A/2)/sin^2(π/2-A/2)-sin^2(π-A/2)
=[-cos2A-1](-sinA/2)cos(A/2)/[cos^2(A/2)-sin^2(A/2)]
=[-2cos^2A+1-1]*(-1/2sinA)/[cosA]
=sinAcosA
=1/2*sin2A
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