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 [latex]\frac { a }{ SinA } =\frac { b }{ SinB } =\frac { c }{ SinC } [/latex] 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 [latex]A=\frac { 1 }{ 2 } abSinC[/latex] 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.

July 6, 2019

Earlier this week, my school took part in a trial OFSTED inspection as part of getting ready for the new inspection framework in September 2019. This involved three Lead Inspectors visiting our school over the course of two days. The first day involved a ‘deep dive’ by each of the Lead Inspectors into Mathematics, English […]

June 30, 2019

The method of how to solve quadratics by factorising is now part of the foundational knowledge students aiming for higher exam grades are expected to have. Here is an example of such a question. Solve x2 + 7x – 18 = 0 In my experience of teaching and marking exam papers students often struggle with […]

June 24, 2019

When learning how to write 3-part ratios students need to understand how ratios can be made equivalent. The start of the lesson reminds students by asking which of six ratios is the odd one out. This is presented to the class as they come into the lesson. Writing Equivalent Ratios A few students immediately go […]

## Sahil Roy says:

<3

Thnks

^^