Use the Pythagorean theorem a+b+c

|a|² = |b|² + |c|²

Step-by-step explanation:

the pythagoras theorem states that in a right angled triangle, the square of the sum of the hypotheneus side is equal to the sum of squares of the opposite side and adjacent side.

That is,

| HYPOTHENEUS|² = |OPPOSTITE|²  + | ADJACENT|²

inorder to use the pythagorean theorem to evaluate this

|a|² = |b|² + |c|²

to complete this square you have to rotate about the origin 270 degrees clockwise.