等腰△ABC内A为顶角,已知sinB=8/17 求cosA sinB tanA△ABC中 已知cosA =15/17 cosB=9/41 求cosC
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![等腰△ABC内A为顶角,已知sinB=8/17 求cosA sinB tanA△ABC中 已知cosA =15/17 cosB=9/41 求cosC](/uploads/image/z/7934844-12-4.jpg?t=%E7%AD%89%E8%85%B0%E2%96%B3ABC%E5%86%85A%E4%B8%BA%E9%A1%B6%E8%A7%92%2C%E5%B7%B2%E7%9F%A5sinB%3D8%2F17+%E6%B1%82cosA+sinB+tanA%E2%96%B3ABC%E4%B8%AD+%E5%B7%B2%E7%9F%A5cosA+%3D15%2F17+cosB%3D9%2F41+%E6%B1%82cosC)
等腰△ABC内A为顶角,已知sinB=8/17 求cosA sinB tanA△ABC中 已知cosA =15/17 cosB=9/41 求cosC
等腰△ABC内A为顶角,已知sinB=8/17 求cosA sinB tanA
△ABC中 已知cosA =15/17 cosB=9/41 求cosC
等腰△ABC内A为顶角,已知sinB=8/17 求cosA sinB tanA△ABC中 已知cosA =15/17 cosB=9/41 求cosC
①等腰△ABC内A为顶角,sinB=8/17,得 0<B=C<π/4 A=π-2B>π/2
∴ cosB=15/17 sinA=sin2B=2sinBcosB=240/289 cosA=-161/289
tanA=sinA/cosA=-240/161 cosA*sinB*tanA=sinB*sinA=1920/4913
②由cosA =15/17 cosB=9/41,得 sinA=8/17 sinB=40/41
∴ cosC=cos[π-(A+B)]=-cos(A+B)=-cosAcosB+sinAsinB=185/697
(1)等腰△ABC内A为顶角,sinB=8/17,得 0<B=C<π/4 A=π-2B>π/2 ∴ cosB=15/17 , sinA=sin2B=2sinBcosB=240/289 , cosA=-161/289 tanA=sinA/cosA=-240/161 , cosA*sinB*tanA=sinB*sinA=1920/4913 (2)由cosA =15/17 cosB=9/41,得 sinA=8/17 , sinB=40/41 ∴ cosC=cos[π-(A+B)]=-cos(A+B)=-cosAcosB+sinAsinB=185/697
等腰△ABC内A为顶角,sinB=8/17,得 0<B=C<π/4 A=π-2B>π/2∴ cosB=15/17 , sinA=sin2B=2sinBcosB=240/289 , cosA=-161/289 tanA=sinA/cosA=-240/161 , cosA*sinB*tanA=sinB*sinA=1920/4913(2)由cosA =15/17 ...
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等腰△ABC内A为顶角,sinB=8/17,得 0<B=C<π/4 A=π-2B>π/2∴ cosB=15/17 , sinA=sin2B=2sinBcosB=240/289 , cosA=-161/289 tanA=sinA/cosA=-240/161 , cosA*sinB*tanA=sinB*sinA=1920/4913(2)由cosA =15/17 cosB=9/41,得 sinA=8/17 , sinB=40/41∴ cosC=cos[π-(A+B)]=-cos(A+B)=-cosAcosB+sinAsinB=185/697
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