Trigonometric ratios

Objective. Use sine, cosine and tangent to find sides and angles.

1. Learn
2. Worked example
3. Practice
4. Feedback
5. Continue

Learn: the key idea

Label the sides opposite, adjacent and hypotenuse relative to the angle, then choose the ratio containing the two sides you care about.

Worked example

Find x where the angle is 35° and the hypotenuse is 12, with x opposite.

1 $sin 35° = x / 12.$
2 $x = 12 \times sin 35°.$

Answer: x ≈ 6.88

Concept mastery

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Practice

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Common mistake. Leaving the calculator in radians during a degrees question.

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