Projection Math Example 1

Follow the full solution, then compare it with the other examples linked below.

Example 1

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Find the orthogonal projection of point P(3,7)P(3, 7) onto the xx-axis, the yy-axis, and the line y=xy = x.

Solution

  1. 1
    Step 1: Projection onto the xx-axis: drop a perpendicular to the xx-axis. The image is (3,0)(3, 0).
  2. 2
    Step 2: Projection onto the yy-axis: drop a perpendicular to the yy-axis. The image is (0,7)(0, 7).
  3. 3
    Step 3: Projection onto y=xy = x: the projection of (x0,y0)(x_0, y_0) onto y=xy = x is (x0+y02,x0+y02)=(5,5)\left(\dfrac{x_0+y_0}{2}, \dfrac{x_0+y_0}{2}\right) = \left(5, 5\right).

Answer

Onto xx-axis: (3,0)(3, 0); onto yy-axis: (0,7)(0, 7); onto y=xy = x: (5,5)(5, 5).
Orthogonal projection drops a perpendicular from the point to the target line. The projection onto y=xy=x uses the formula where the projected point lies on the line at the foot of the perpendicular from PP.

About Projection

The image formed when points of a shape are mapped onto a lower-dimensional surface along parallel or converging rays.

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