Let $a_1$, $a_2$, $\dots$, $a_{12}$ be twelve equally spaced points on a circle with radius 1. find\[(a_1 a_2)^2 + (a_1 a_3)^2 + \dots + (a_{11} a_{12})^2.\](the sum includes the square of the distance between any pair of points, so the sum includes $\binom{12}{2} = 66$ terms.)

The sum evaluates to 144. See the linked question in the comments for details.

step-by-step explanation:

1. practice, practice & more practice

2. review errors

3. master the key concepts

do not try to memorise the processes.

4. understand your doubts.

5. create a distraction free study environment

6. create a mathematical dictionary

7. apply maths to real world problems.

cut 138 centimeters off

step-by-step explanation:

250-112 = 138