cos15°等于多少构造一个特殊的角三角形如下:直角三角形ABC,A=90度 B=30度 C=60度延长AB到D,使得BD=BC,则此时角D为15度.设AC=1,则BC=2,BD=BC=2,AB=根号3,AD=根号3+2,CD=根号2+根号6,cos15=cos角D=AD/CD=(根号3+2)/(
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![cos15°等于多少构造一个特殊的角三角形如下:直角三角形ABC,A=90度 B=30度 C=60度延长AB到D,使得BD=BC,则此时角D为15度.设AC=1,则BC=2,BD=BC=2,AB=根号3,AD=根号3+2,CD=根号2+根号6,cos15=cos角D=AD/CD=(根号3+2)/(](/uploads/image/z/965478-30-8.jpg?t=cos15%C2%B0%E7%AD%89%E4%BA%8E%E5%A4%9A%E5%B0%91%E6%9E%84%E9%80%A0%E4%B8%80%E4%B8%AA%E7%89%B9%E6%AE%8A%E7%9A%84%E8%A7%92%E4%B8%89%E8%A7%92%E5%BD%A2%E5%A6%82%E4%B8%8B%EF%BC%9A%E7%9B%B4%E8%A7%92%E4%B8%89%E8%A7%92%E5%BD%A2ABC%2CA%3D90%E5%BA%A6+B%3D30%E5%BA%A6+C%3D60%E5%BA%A6%E5%BB%B6%E9%95%BFAB%E5%88%B0D%2C%E4%BD%BF%E5%BE%97BD%3DBC%2C%E5%88%99%E6%AD%A4%E6%97%B6%E8%A7%92D%E4%B8%BA15%E5%BA%A6.%E8%AE%BEAC%3D1%2C%E5%88%99BC%3D2%2CBD%3DBC%3D2%2CAB%3D%E6%A0%B9%E5%8F%B73%2CAD%3D%E6%A0%B9%E5%8F%B73%2B2%2CCD%3D%E6%A0%B9%E5%8F%B72%2B%E6%A0%B9%E5%8F%B76%2Ccos15%3Dcos%E8%A7%92D%3DAD%2FCD%3D%28%E6%A0%B9%E5%8F%B73%2B2%29%2F%28)
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