admin百科知識 2022-02-12 23:04:23 已知cos(π4-a)=35,sin(5π4+b)=-1213,a∈(π4,3π4)b∈(0,π4),求sin(a+b)值已知cos(π/4-a)=3/5,sin(5π/4 b)=-12/13,a∈(π/4,3π/4)b∈(0,π/4),求sin(a b)值網友廻答：匿名網友a∈(π/4,3π/4)π/4-a∈(-π,0)sin(π/4-a)0sin²(π/4 b) cos²(π/4 b)=1cos(π/4 b)=5/13sin(a b)=sin[(π/4 b)-(π/4-a)]=sin(π/4 b)cos(π/4-a)-cos(π/4 b)sin(π/4-a)=16/65 db標簽 生活常識_百科知識_各類知識大全»已知cos(π4-a)=35,sin(5π4+b)=-1213,a∈(π4,3π4)b∈(0,π4),求sin(a+b)值
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