Chp 8 Workbook
Chp 8 Workbook
Chp 8 Workbook
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NAME DATE PERIOD<br />
8-4<br />
Enrichment<br />
Sine and Cosine of Angles<br />
The following diagram can be used to obtain approximate values for the sine and cosine of<br />
angles from 0° to 90°. The radius of the circle is 1. So, the sine and cosine values can be<br />
read directly from the vertical and horizontal axes.<br />
90°<br />
1<br />
80°<br />
70°<br />
0.9<br />
60°<br />
0.8<br />
50°<br />
0.7<br />
40°<br />
0.6<br />
0.5<br />
30°<br />
0.4<br />
20°<br />
0.3<br />
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.<br />
0.2<br />
0.1<br />
0<br />
0°<br />
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1<br />
Example Find approximate values for sin 40° and<br />
cos 40°. Consider the triangle formed by the segment<br />
marked 40°, as illustrated by the shaded triangle at right.<br />
sin 40° = −<br />
a c ≈ −<br />
0.64<br />
1 or 0.64 cos 40° = −<br />
b c ≈ −<br />
0.77 or 0.77<br />
1<br />
1. Use the diagram above to complete the chart of values.<br />
x° 0° 10° 20° 30° 40° 50° 60° 70° 80° 90°<br />
sin x° 0.64<br />
cos x° 0.77<br />
10°<br />
1<br />
0.64<br />
0<br />
x°<br />
c = 1 unit<br />
a = sin x°<br />
40°<br />
b = cos x° 0.77 1<br />
Lesson 8-4<br />
2. Compare the sine and cosine of two complementary angles (angles with a<br />
sum of 90°). What do you notice?<br />
Chapter 8 29 Glencoe Geometry
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