已知sin=[(-π/2) -α]*cos[(-5π/2)-α]=60/169,且45°
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![已知sin=[(-π/2) -α]*cos[(-5π/2)-α]=60/169,且45°](/uploads/image/z/3749076-36-6.jpg?t=%E5%B7%B2%E7%9F%A5sin%3D%5B%28-%CF%80%2F2%29+-%CE%B1%5D%2Acos%5B%28-5%CF%80%2F2%29-%CE%B1%5D%3D60%2F169%2C%E4%B8%9445%C2%B0)
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已知sin=[(-π/2) -α]*cos[(-5π/2)-α]=60/169,且45°
已知sin=[(-π/2) -α]*cos[(-5π/2)-α]=60/169,且45°
已知sin=[(-π/2) -α]*cos[(-5π/2)-α]=60/169,且45°
sin[(-π/2) -α]*cos[(-5π/2)-α]=60/169
-cosα(-sinα)=60/169
∴cosαsinα=60/169
∵45°0
∵sin²α+cos²α=1
∴1+2cosαsinα=1+120/169=289/169
∴(sinα+cosα)²=289/169
∴sinα+cosα=17/13 ①
1-2cosαsinα=1+120/169=49/169
∴(sinα-cosα)²=49/169
∴sinα-cosα=7/13 ②
①②解得:
sinα=12/13,cosα=5/13