Question

在四边形ABCD中,AB//CD,∠A=90°CD=2,AB=3,AD=7,P为AD上一点,CP⊥BP,求DP长

Answer 1

dp=x, ap=7-x;

2^2+x^2+(7-x)^2+3^2=7^2+(3-2)^2;

then solve the x.