Question 140509
Angles can be measured in different units just like length can be measured in inches and in millimeters (and a lot of other units). 
Two commonly used units are degrees and radians.
A circle, like a clock, sweeps 360 degrees. 
In radians, it would be {{{2(pi)}}} radians.
So the conversion factor is  {{{2(pi)/360}}} to go from degrees to radians.
The conversion factor to go from radians to degrees is {{{360/(2(pi))}}}.
The angle A is {{{(pi)/10}}} radians or 18 degrees.
Let's call the side oppposite angle A, side b.
Let's call the side adjacent (next to) angle A, side a.
Side c is the hypotenuse of the right triangle.
From trignometry,
{{{sin(A)=b/c}}}
{{{b=c*sin(A)}}}
{{{b=43.8*sin(18)}}}
{{{b=43.8*0.3090}}}
{{{b=13.53}}}
Since it's a right triangle, you can use the Pythagorean theorem to find a.
{{{a^2+b^2=c^2}}}
{{{a^2+(13.5)^2=(43.8)^2}}}
{{{a^2+183.19=1918.44}}}
{{{a^2=1735.25}}}
{{{a=41.66}}}
You could have also use the cos(A).
{{{cos(A)=a/c}}}
{{{a=c*cos(A)}}}
{{{a=43.8*cos(18)}}}
{{{a=43.8*0.9511}}}
{{{a=41.66}}}
a=41.66
b=13.53