Please help I can't figure this out ​

We can use the sine law to find P1 P2

By the sine law, P1 P2 = sin 15.  We can also find P1 P_3 = sin 60, P1 P4 = sin 90, etc.

So (P1 P2)^2 + (P1 P3)^2 + … + (P11 P12)^2 = 12 (sin 15)^2 + 12 (sin 30)^2 + 12 (sin 45)^2 + … + 12 (sin 90)^2 = 42.

I think It's 12^2=144 am I right?

A regular dodecahedron $P_1 P_2 P_3 \dotsb P_{12}$ is inscribed in a circle with radius 1.
Compute  $(P_1 P_2)^2 + (P_1 P_3)^2 + \dots + (P_{11} P_{12})^2$.
(The sum includes all terms of the form $(P_i P_j)^2$, where $1 \le i < j \le 12$.

My answer see here: https://web2.0calc.com/questions/plshelp#r7