g A spotlight on the ground is shining on a wall 20m away. If a woman 2m tall walks from the spotlight toward the building at a speed of 0.8m/s, how fast is the length of her shadow on the building decreasing when she is 4m from the building

0.3 m/s

Step-by-step explanation:

As the two triangles in the diagram are similar to each other we have

Again as the triangles are similar we have

Differentiating the above equation with respect to time we get

The speed at which the shadow is changing is 0.3 m/s.