First we look at the inner part:
That asks for the angle between and whose sine
is .
Since we know that ,
we draw such an angle by placing a right triangle
in the first quadrant whose angle at the origin is such that its
opposite side is y=1 and its hypotenuse is r=7, like this:
The angle indicated by the red arc is the angle: .
To find the tangent, we must calculate the adjacent side x,
using the Pythagorean theorem:
So we now have all three sides of the right triangle:
The problem is
and since we know that .
Edwin