Didn't know if this was the right category to put this into but anyway.
I got the following problem. There is a lantern that has a height of 11 meters
a man with a height of 2.20 meters is standing at the lantern's base. The man starts moving away from the lantern with a velocity of v=2 m/s. I need to find with what velocity his shadow grows. Please this is urgent. Thx from now.
Now if you see the diagram you made, notice that there are two right triangles in the picture, one with base "y" and height 2.20, the other with base "x+y" and and height 11. These two triangles are similar triangles and their angles are the same so that their ratios of their corresponding edges should be equal:
The rate of change of the length of the shadow is the derivative of y. So we want to find . Since he is moving away from the lantern at 2 m/s, we know that (if he was moving towards the lantern it'd be -2)
Now you must differentiate the general equation implicitly
Do you see how it's done?