1. ALWAYS work with 1st Quad then translateC A S T 0o
180o
270o
90o
180o - xo
180o + xo xo
360o + xo
CAST diagram
Exact Values
Solving Trig Equations
Example θ
Find x coordinates for A and B A B
0.4
Solve: tanxo + 1 = 0
tanxo = -1
xo = tan-1 (1)
xo = 45o
sinxo = 0.4
xo = sin-1 (0.4)
Solution : xo = 180o - 45o = 135o
xo = 23.6o
xo = 360o - 45o = 315o
xo =180o o = 156.4o

2. Solving Trig Equations
Graphically what are we trying to solve C A S T 0o
180o
270o
90o  
Example 5 Type 4 :
Solving the equation cos2x = 1 in the range 0o to 360o
cos2 xo = 1
cos xo = ± 1
cos xo = 1
xo = 0o and 360o
cos xo = -1
xo = 180o
created by Mr. Lafferty