Hi Stacy M

Always draw yourself a diagram and if you have a picture please present it. Since your description says the 15 m pole is leaning, this sounds like a hypotenuse. It also says the foot of the pole is 10 m I'll take that to mean the bottom of the pole on the ground is 10 m away from the wall on the ground.

If that correctly describes your situation and you have a Right Triangle all you need do is

Determine which ratio applies

There are only two

Set that ratio up

Use a calculator with an Inverse Function to find angle whose Sine or Cosine is

Adjacent/Hypotenuse = Cosine of your angle

Opposite/Hypotenuse = Sine of your angle

Give it a try if you have any questions just send me a message and I will try to help further.