Dear Expert mathematicain,
what is the fundamentaal law of trigonometry?
By "fundamental theorem of trigonometry" is often meant sin2(x) + cos2(x) = 1, it is actually the Pythagorean Theorem. if you have a right triangle with a hypotenuse of one, sin(x) is one leg, and cos(x) is the other. The Pythagorean Theorem states that a2 + b2 = c2 and therefore sin2(x) + cos2(x) = 1.