Rotation of 270° ,counterclockwise
Find center point of triangle
JK = √ 9^2 +5^2
. = √ 106
JL = √9^2 + 3^2
. = √90
KL = 8
Then now find point J'
Distance from J to origin = JO = √4^2+2^2 =√20
Angle is arctan (2/4) = 26.56°
Then new coordinates J' are
Angle 270+26.56 = 296.56°
From origin trace a line perpendicular to JO
then
y = √20• Cos 26°
y = 4