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Contents
Ratio for Acute Angles
Ratio for Complementary Angles
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Trigonometry
Ratio of Acute Angles The hypotenuse is defined as the longest side of a right-angled triangle. It is the one across the right angle. Look at angle a of the yellow triangle. The opposite is the side opposite the angle you are finding. The other side is known as the adjacent. But let's say you are looking at the other angle, then the opposite side and adjacent side will change. For this right angled triangle, the
constant ratio constant
ratio constant
ratio
Example
1
a = tan-1 ¾
or a
= cos-1 4/5 or a
= sin-1 3/5
By
pressing your calculator, you should get 36.869...° If not, you will need to
change the mode of your calculator to degree.
Example 2
x = 18 cos 47°
= 12.28 cm
Example 3
y = 25 cos 32°
= 21.20 cm
tan 32°
= x/y = x/21.2
= 21.2
tan 32°
= 13.25
cm
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is called the sine of angle a
is called the cosine of angle a
is called the tangent of angle a
Look at the figure on the right. Find Ða.
tan a = ¾ or cos a
= 4/5 or sin a
= 3/5
