One thing you should notice is that the transverse line and the parallel line form a right triangle. We are told that the base is 4 and the angle between the hypotenuse and the leg is 45°
From this we can solve for the second leg. Here's the list of trig functions
sinФ = opposite/hypotenuse
cosФ = adjacent/hypotenuse
tanФ = opposite/adjacent
Since we are only given the adjacent and we are trying to solve for the opposite leg, we can deduce we use tanФ. So we get
[tex]tan45 = x/4[/tex]
Multiply by 4 to isolate x and we get
[tex]4*tan45[/tex] = x
Hopes this helps!
