高考问答绝地求生跳废墟箱子:证明下列各式
来源：百度文库 编辑：高考问答 时间：2024/05/03 01:55:26
2sin（a+派/4）cos（b+派/4）=cos（a+b）+sin（a-b）
2sin（a+45）sin（a-45）=sin^2a-cos^2a
cos(A+B)+sin(A-B)=(cosA+sinA)(cosB-sinB)
cos(A-B)-sin(A+B)=(cosA-sinA)(cosB-sinB)
sin(a+b)cos(a-b)=sinacosa+sinbcosb
2sin（a+45）sin（a-45）=sin^2a-cos^2a
cos(A+B)+sin(A-B)=(cosA+sinA)(cosB-sinB)
cos(A-B)-sin(A+B)=(cosA-sinA)(cosB-sinB)
sin(a+b)cos(a-b)=sinacosa+sinbcosb
2sin（a+派/4）cos（b+派/4）
=sin(a+π/4+b+π/4)+sin(a+π/4-b-π/4)(积化和差)
=sin(a+b+π/2)+sin(a-b)
=cos（a+b）+sin（a-b）
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2sin（a+45）sin（a-45）
=-cos(a+45+a-45)+cos(a+45-a+45)
=-cos2a
=sin^2a-cos^2a
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(cosA+sinA)(cosB-sinB)
=cosAcosB-sinAsinB+sinAcosB-cosAsinB
=cos(A+B)+sin(A-B)
--------------------------
(cosA-sinA)(cosB-sinB)
=cosAcosB+sibAsinB-sinAcosB-cosAsinB
=cos(A-B)-sin(A+B)
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sin(a+b)cos(a-b)
=1/2*(sin(a+b+a-b)+sin(a+b-a+b))(积化和差)
=1/2*(sin2a+2in2b)
=sinacosa+sinbcosb