its 42 degrees
its a proportionate line so it has the same angle on both sides.
triple angle formulas are these:
each of the six trig functions is equal to its co-function evaluated at the complementary angle. periodicity of trig functions. sine, cosine, secant, and cosecant have period 2π while tangent and cotangent have period π. identities for negative angles.
let's solve for y.
step 1: add 9x to both sides.
step 2: divide both sides by -2.