Without doing any calculus of an integral containing a sine, verify that . My idea was by bounding the integral to get something greater but still lesser than . So I thought about bounding this way : , which is unfortunately greater than . I have no other idea of how to procede. Any idea is welcome.
If I'm not wrong, it's ! Nice graphic. It verifies graphically the relation we must verify. Now I'm asking if it's possible to verify it algebraically or any other way that respect the condition "Without doing any calculus of an integral containing a sine", or course not a cosine, or something similar. (I'm asking this because I'm more than sure it's what the expect from us to do).