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.