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The side opposite the right angle is called the hypotenuse.
It is the largest side of a right-angled triangle.
If you stand at A in the triangle ABC, the side BC
is opposite to you and the side AB is next to you. We
therefore say that BC is the opposite side to angle A
and AB is the adjacent side to angle A.
Notation
Trigonometric Ratios
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If you have trouble remembering the definitions, just remember SOH
CAH TOA.
Using a Graphics Calculator
If you have a TI-83 graphics calculator, select Degree
from the MODE menu and set Float
to 4 to obtain the answers correct to 4 decimal places. Press QUIT
to return to the Home Screen and clear the
screen if necessary.
If you are using another calculator, consult its instruction booklet or
ask your teacher how you can set its Mode to 'Degree mode' and the decimal
places display to 4 places.
Example 1
Evaluate the following to 4 decimal places:
Solution:
Recall that:
This is abbreviated as follows:
Example 2
Solution:
Note:
Key Terms
hypotenuse, opposite side, adjacent
side, theta, trigonometric
ratios, sine, sin, cosine,
cos, tangent, tan,
SOH, CAH, TOA,
SOH CAH TOA, degrees, minutes,
seconds
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