已知过点P(1,2)的直线与圆x²+y²+2x-6y+5=0相切,且与直线ax+y-1=0垂直,则a=__
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![已知过点P(1,2)的直线与圆x²+y²+2x-6y+5=0相切,且与直线ax+y-1=0垂直,则a=__](/uploads/image/z/13337037-45-7.jpg?t=%E5%B7%B2%E7%9F%A5%E8%BF%87%E7%82%B9P%EF%BC%881%2C2%EF%BC%89%E7%9A%84%E7%9B%B4%E7%BA%BF%E4%B8%8E%E5%9C%86x%26%23178%3B%2By%26%23178%3B%2B2x-6y%2B5%3D0%E7%9B%B8%E5%88%87%2C%E4%B8%94%E4%B8%8E%E7%9B%B4%E7%BA%BFax%2By-1%3D0%E5%9E%82%E7%9B%B4%2C%E5%88%99a%3D__)
已知过点P(1,2)的直线与圆x²+y²+2x-6y+5=0相切,且与直线ax+y-1=0垂直,则a=__
已知过点P(1,2)的直线与圆x²+y²+2x-6y+5=0相切,且与直线ax+y-1=0垂直,则a=__
已知过点P(1,2)的直线与圆x²+y²+2x-6y+5=0相切,且与直线ax+y-1=0垂直,则a=__
如果a=0,显然是满足条件的.
如果a不等于0,设切线的方程是y=(1/a)x+b
过P点得到方程1:1/a+b=2
圆心(-1,3)到切线的距离等于半径得到方程2:|(-1/a+b-3)|/(1+1/a^2)^(1/2)=2
解出来a=4/3 所以a=0或者4/3