Trigonometry Section 7.4 Find the sine and cosine of special angles. Consider the angles 20 o and 160 o Note: sin 20 o = sin160 o and cos 20 o = -cos 160 o 20 o is the reference angle for 160 o The acute angle α is the reference angle for the angles, 180 – α, α, and 360 –α. Note: 20 o is the reference angle for 160 o, 200 o, and 340 o

Find the reference angle 120 o 190 o 4

Express in terms of the reference angle sin 128 o cos 128 o sin -37 o cos 5.2

Use a calculator to find each value sin 32 o cos 107 o sin 4.61 cos -6.42

Special triangles

Find the indicated value sin 30 o cos 60 o sin 120 o cos 135 o sin 225 o cos sin

Graphs of trigonometric functions

assignment Page 279 Problems 2 – 10 even, all