6.2 Solving Trigonometric Equations with Identities

sin 2 2 cos 0 0 360o

• If you see a trig function of a double angle and another trig function of a single angle, try using the double angle formula.

cos 2 3sin 2 0 360o

0 360o 24cos 4sin 5 0

• If you see two different trig functions and one is being squared, try using a pythagorean identity to get the equation in terms of one trig function.

0 360o sin cos 1

• Try squaring both sides when the previous two hints don’t apply. Because you can’t get sine in terms of cosine, but you can get sine squared in terms of cosine squared. Don’t forget to check for extraneous solutions.

• Also, you can try using the ratio and reciprocal identities (#5 on WS 6.2)