Answer:
75
Explanation:
Since we know ABCD is a square, then we know that all the angles (of the edges) are 90 degrees. So, if you look at angle C you can see it already gives you 60 degrees so just subtract it from 90 since that is what the full measure of the angle is. You should be left with 30. Since the triangle of the angle you are trying to find is a isosceles triangle, you only need 1 angle. All measures of an angle equal to 180 so subtract your 30 from that 180 and you will be left with 150. Both of the angles are the same so just divide 150 by 2 and you will get 75. I'm sorry if this doesn't make much sense, I'm currently in geometry too so I'm still learning. I hope this helps!