Angles are measured in degrees. A few examples will show you how to measure angles:
The sides of a square meet at 90 degrees: (The little square means 90 degrees)
Here, the two lines meet at 30 degrees:
Here's an obtuse angle of 155 degrees:
Now, here's a problem for you:
What angle do these lines meet at?
Hint: It's half of the 90 degree angle!