2、x^2+(y+20.7)^2=27.9^2

3/ The bridge equation is x 2+(y+10.5) 2 =14.52.

X=-5，y = 3. 1 & gt； 3 cans

4. Establish the system with BC as the X axis B as the origin, and get the abc coordinates.

Write the equation of the slope of AD, be and the intersection point P( 15/7, 3 and 3/7)- root 3/9, and then

AD，PC=— 1