Page 6 - Dahlia Oktaviani Ginting Buku

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1.3 Trigonometric Comparison of Special Angles

0
The special angles (special angles) in question are 0 ,
0
0
0
0
30 , 45 , 60 , and 90 .

0
a. 45 angle
Look at the following triangle

c a
45
0
A b C
 ABC right angles at C and BAC = 45 .
0
0
0
Because BAC = 45 then ABC = 45 , so that
 ABC is an isosceles right triangle (a = ) b .
2
2
2
2
2
c = a + b c = 2a
2
2
2
2
c = a + a c = 2a = a 2

The trigonometric ratios are obtained:
a a
0
sin 45 = = = 1 2
c a 2 2
b a
0
cos 45 = = = 1 2
c a 2 2
a a
tan 45 = = = 1
0
b a

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