已知sin(A+π/4)+sin(A-π/4)=根号2/3 1.求sinA的值 2.求【sin(A-π/4)】/【1-cos2A-sin2A】的值 谢
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![已知sin(A+π/4)+sin(A-π/4)=根号2/3 1.求sinA的值 2.求【sin(A-π/4)】/【1-cos2A-sin2A】的值 谢](/uploads/image/z/1583291-11-1.jpg?t=%E5%B7%B2%E7%9F%A5sin%28A%2B%CF%80%2F4%29%2Bsin%28A-%CF%80%2F4%29%3D%E6%A0%B9%E5%8F%B72%2F3+1.%E6%B1%82sinA%E7%9A%84%E5%80%BC+2.%E6%B1%82%E3%80%90sin%28A-%CF%80%2F4%29%E3%80%91%2F%E3%80%901-cos2A-sin2A%E3%80%91%E7%9A%84%E5%80%BC+%E8%B0%A2)
已知sin(A+π/4)+sin(A-π/4)=根号2/3 1.求sinA的值 2.求【sin(A-π/4)】/【1-cos2A-sin2A】的值 谢
已知sin(A+π/4)+sin(A-π/4)=根号2/3 1.求sinA的值 2.求【sin(A-π/4)】/【1-cos2A-sin2A】的值 谢
已知sin(A+π/4)+sin(A-π/4)=根号2/3 1.求sinA的值 2.求【sin(A-π/4)】/【1-cos2A-sin2A】的值 谢
(1)展开,得sinAcosπ/4 + cosAsinπ/4 + sinAcosπ/4 - cosAsinπ/4=2sinAcosπ/4=√2×sinA=√2/3
所以,sinA=1/3.
(2) 原式=[sinAcosπ/4 - cosAsinπ/4]/[2sin^A-2sinAcosA]=[√2/2]/2sinA=3√2/4.