Prove zeta(2) by interesting double integral

Hi! I am Isaac and it is the first time for me to send a video idea to you! I got a set of problems that can help prove zeta(2)=pi^2/6 which is very interesting! Here is the problem set:

I have watched your video for 2-3 years and your videos are very interesting and fun, especially Math for Fun! Even I made a account of Brilliant and made some questions and discussion because of you! I will be so glad if you make a video about this.

P.S. My English is pretty bad cuz I am come from HK. Sorry about that.