Even integrand over a symmetric integral

Help me create more free content! =) https://www.patreon.com/mathable Interested in burning stuff using flammy lasers?! Check out Diodica and get free shipping on your order: https://diodica.com/discount/papaflammy Just a quick little proof regarding integrals =) It's an important identity so always keep it in the back of your head! =) Twitter: https://twitter.com/FlammableMaths Facebook: https://www.facebook.com/flammablemaths/ Visit my website! =) https://mathable.me/