求由点(3,2)向圆x2 +y2-4x+2y-4=0所引的切线长.
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![求由点(3,2)向圆x2 +y2-4x+2y-4=0所引的切线长.](/uploads/image/z/8563576-40-6.jpg?t=%E6%B1%82%E7%94%B1%E7%82%B9%283%2C2%29%E5%90%91%E5%9C%86x2+%2By2-4x%2B2y-4%3D0%E6%89%80%E5%BC%95%E7%9A%84%E5%88%87%E7%BA%BF%E9%95%BF.)
求由点(3,2)向圆x2 +y2-4x+2y-4=0所引的切线长.
求由点(3,2)向圆x2 +y2-4x+2y-4=0所引的切线长.
求由点(3,2)向圆x2 +y2-4x+2y-4=0所引的切线长.
x² +y²-4x+2y-4=0
(x-2)²+(y+1)²=9
圆心是(2,-1),半径是3
定点到圆心距离
=√[(3-2)²+(2-(-1))²]
=√10
切线长
=√(√10²-3²)
=1