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.

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