With respect to the 50 degree angle, the side x is the opposite leg. It is the leg furthest from the reference angle. The hypotenuse is 5 meters.
The trig function sine ties together the opposite and hypotenuse
sin(angle) = opposite/hypotenuse sin(50) = x/5 5*sin(50) = x .... multiply both sides by 5 x = 5*sin(50)
------------------
Since x = 5*sin(50) isn't listed as an answer choice, let's try using cosine. We can't use it right away because we don't know the adjacent side. What we can do is change the reference angle. The missing angle of the triangle is 90-50 = 40 degrees. Let's make the 40 degree angle the reference angle
So x is now the adjacent side with respect to the 40 degree reference angle. The hypotenuse is always the longest side. The hypotenuse stays at 5.
cos(angle) = adjacent/hypotenuse cos(40) = x/5 5*cos(40) = x x = 5*cos(40)
