Let us have a certain function like $f(x)=x$
In the world of integration, can I say that $\int_{0}^bxdx=\frac{1}{2}(b)(f(b))$? Because if you look at graph of function x, it would look like something 45° right triangle (though we can probably change its angle using the trig func $\tan$ and multiplying it by x like this $f(x)=x\tan(s°)$ or in integration $\int_{0}^bx\tan(s°)dx=\frac{1}{2}(b)(b\tan(s°))$ or making it more complicated $\int_{a}^bx\tan(s°)dx=(\frac{1}{2}(b)(b\tan(s°)))-\frac{1}{2}(a)(f(a))$ where s° is your/the preferred angle.
Note: we're using degrees in tan not radian.