同学们一定遇到过这样一些问题,乍看似乎与圆没有什么联系,而解答时添加辅助圆(隐形圆)却能使问题迎刃而解.那么如何让“隐形圆”现形呢?一、把直角看作“隐形圆”的切线与过切点的半径构成的角例1已知在正方形ABCD中,CD=2,若点P满足PD=1,且∠BPD=90°,求点A到BP的距离.解:∵PD=1,∠BPD=90°,∴BP是以点D为圆心、以1为 Students must have encountered such problems, at first glance, it seems that there is no connection with the circle, and the answer to add the auxiliary circle (invisible circle) can solve the problem. So how to make “Invisible Circle Corner angle is taken as the angle formed by the tangent and tangent radius of ”Invisible Circle ". Example 1 It is known that CD = 2 in a square ABCD, and if the point P satisfies PD = 1 and ∠BPD = 90 ° A to BP. Solution: ∵PD = 1, ∠BPD = 90 °, ∴BP is the point D as the center, with 1