Some days ago, I read a mathematics magazine and I came across over a very interesting problem:

Given a function f(x) that is even and continuous on [-1,1] and

Find the value of :

I think it has something to do with properties of even functions but I'm not sure how to use it. Can somebody help me with this problem?

Yes, this video explains it. https://youtu.be/gK8Wf9ZkZW4

Thanks!