So the rectangular coordinates of A are (2cos(π/3), 2sin(π/3)), that is, (1, √3).
B (-2,0) and C( 1, -√3) can be obtained in the same way.
(2)|PA|^2+|PB|^2+|PC|^2
=(2cosφ- 1)^2+(3sinφ-√3)^2+(2cosφ+2)^2+(3sinφ-0)^2+(2cosφ- 1)^2+(3sinφ+√3)^2
= 12(cosφ)^2+27(sinφ)^2+ 12
= 15(sinφ)^2+24
By 0
(In fact, you can directly Baidu this question, and the answer will come out. )