All three of the trigonometric functions of an angle are related If we know the value of one of the three, we can calculate the other two (up to sign) by using the Pythagorean and tangent identities We do not need to find the angle itself in order to do this We need only know in which quadrant the angle lies to determine the correct sign for the trig ratios Example 555 If \(~\sin \thetaTan(x y) = (tan x tan y) / (1 tan x tan y) sin(2x) = 2 sin x cos x cos(2x) = cos 2 (x) sin 2 (x) = 2 cos 2 (x) 1 = 1 2 sin 2 (x) tan(2x) = 2 tan(x) / (1For any value of \(x\), this equation is true Trig identities are sort of like puzzles since you have to
How I Remember Trig Identities Part 2 Beyond Solutions
