Find the length of the projection of on .
Step 1: Find the length of . Use Pythagoras' theorem.
Step 2: Find the length of .
For any right-angled triangle, the square of a leg's length is equal to the product of the length of the projection of the leg on the hypotenuse and the length of triangle's hypotenuse.
Step 3: Find the length of .
The projection of on is equal to the length of , so the projection of on is .