OK, so I am revising for an upcoming test and am a bit confused. I have previously learn Trigonometry, however that was around a year ago, and i have completely forgotten it now. I went on to MathsWatch, which is an online revision website. I am currently going through the three trigonometry clips on there (Clips 147a, 147b and 147c). On clip 147a they teach a divisible method 
However, on Clip 147b they teach it using a multiplication method, as follows: 
I cannot, for the life of me, remember as to why two different methods are used. Any explanations?
They use the same equation. What is causing the confusion is the way they depict the formulas. In the first pic, the triangle "shows" the equation as
Equation 1: $A$ = $\cos c$ $*$$H$
while the second pic says:
Equation 2: $\cos c$ = $A$$\div$$H$
Since you are trying to find side A, you have to re-arrange the formulas to solve for A.
In the first pic your equation is already solving for side A so you dont need to rearrange Equation 1.
For the second pic, you have to re-arrange Equation 2 to solve for A.
Equation 2: $\cos$ c = $A$$\div$$H$
$\cos c$ $*$ $H$ = $A$$\div$$H$ * $H$ Multiplying both sides by H
$A$ = $\cos c$ $*$ $H$ <--This is the same as Equation 1