Your Basket 0 items - £0.00

Students learn how to derive the Sine, Cosine and Area formulae for non-right-angled triangles. They use this knowledge to solve complex problems involving triangular shapes.

This unit takes place in Term 5 of Year 10 and follows on from trigonometry with right-angled triangles.

**Prerequisite Knowledge**

- Know the trigonometric ratios Sinϑ = Opp/Hyp, Cosϑ = Adj/Hyp and Tanϑ = Opp/Adj.
- Apply them to find angles and lengths in right-angled triangles and, where possible, general triangles in two and three dimensional figures

**Success Criteria**

- Know and apply the sine rule and cosine rule a
^{2}= b^{2}+ c^{2}– 2bcCosA to find unknown lengths and angles. - Know and apply the formula for the area of a triangle to calculate the area, sides or angles of any triangle.

**Key Concepts**

- The Sine rule is used when:
- Any two angles and a side is known.
- Any two sides and an angle is known

- The Cosine rule is used when:
- all three sides are known
- two sides and the adjoining angle is known

- Students should have the opportunity to derive the three formulae from first principals.
- This topic is often linked with problems involving bearings and map sketches.

**Common Misconceptions**

- Students often have difficulty choosing the correct formula.
- A common mistake is attempting to use Pythagoras’ Theorem to find a length in a non-right angled triangle.
- Marks are often lost when breaking down the Cosine Rule using the order of operations.

Comments are closed.

April 17, 2021

How to teach working out the reciprocal of integers, fractions, decimals and mixed numbers.

April 16, 2021

How to teach proving geometrical properties using algebra.

April 4, 2021

How to teach solving 3D problems using trigonometry.

## Sahil Roy says:

<3

Thnks

^^