As part of leveling the geodesic quadrilateral, I got the need to form a sine conditional equation. I do not understand how it is formed, what is the principle. In the case of a triangle with one central non-starting point.
I know that I follow the pattern in which I take the sine of the angles complementary (adjacent) to the one in the denominator in the numerator, so the quotient will be one in the end. But I don't understand about the quadrilateral.