Basically, if you were to combine methods of these maths formulas, then you would be able to do anything, maybe not as fast in the beginning, but, as you get used to it, much faster and more accurately.
For geometry, one of the golden rules i find is to double all the numbers, so, you make that five a zero, and then you cut it there, then half it again, with a more definite answer for the equation.
So, if you eliminate, give values for and so forth, for the whole equation, it will be so easy you will laugh!