Projection Matrix onto Line

Problem

Build the 2x2 orthogonal projection matrix onto the line through the origin at angle theta degrees.

With c = cos(t) and s = sin(t), P = [[c^2, c*s], [c*s, s^2]]. The matrix is symmetric and idempotent.

Hint

P = u*u^T where u is the unit vector along the line.

case 1

in: [0]

expected: [[1,0],[0,0]]

case 2

in: [90]

expected: [[0,0],[0,1]]

case 3

in: [45]

expected: [[0.5,0.5],[0.5,0.5]]

case 4

in: [30]

expected: [[0.75,0.4330127018922193],[0.4330127018922193,0.25]]

Starter codePython

def projection_matrix_2d(theta_degrees):
    # Your code here
    pass

4 test cases · run your code against them in the editor