Elementary Trigonometry

Theory Refresher

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Trigonometry is all about angles and sides of a right-angled triangle.

Recall that the side of the triangle opposite the right-angle is called the hypotenuse (Hyp). Further, note in the diagram that side

is opposite (Opp) angle

and side

is adjacent (Adj) to angle

Trigonometric Ratios

Reciprocal Ratios

To find the exact value of these ratios for angles 30^o, 45^o and 60^o, read the values from the following key triangles (for other values, use your calculator).

For 45^o:
Isosceles right triangle,
side length 1 For 30^o and 60^o:
Equilateral triangle,
side length 2

Solving problems

Trigonometric ratios can be used to solve problems involving right-angled triangles. In these cases, make sure you draw a diagram and label it carefully.

And do not forget about Pythagoras' Theorem:

(that is, "the square of the hypotenuse is equal to the sum of the squares of the other two sides.")

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Elementary Trigonometry

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