By A Mystery Man Writer
This video explains what the transformation matrix is to rotate 90 degrees anticlockwise (or 270 degrees clockwise) about the origin.
Rotate a matrix by 90 degree without using any extra space
Rotations with Matrices – Guzinta Math
Matrix Rotations
How can an N*N matrix be rotated clockwise and anti-clockwise? - Quora
SOLUTION: Arithmetic, Transformation matrix formula's, reflection, line of reflection, rotation, center of rotation, angle of rotation, direction, clockwise, anti clockwise - Studypool
Math Alive Geometry 1
Understanding Geometric Transformation: Rotation using OpenCV-Python
Creating a rotation matrix in NumPy
90 Degree Anticlockwise Rotation Transformation Matrix