i solved maybe i have wrong.Can you check my solution way?
Thanks and best regards.(i dont know how can use latex so ...)
It seems OK except for one small mistake. I think it should be , NOT . You will need to fix the other mistakes that follow from this. The final numerical answer is unchanged.
Since this is a DEFINITE Integral you should change bounds as you change the variables. There's no need to draw that triangle and figure out the . The t-bounds are trivial, use them instead and it will save you a lot of work and time.