Mon Feb 27th - Introduction to Trigonometry

LEARNING OBJECTIVE: Discover what sine and cosine values are

SUCCESS CRITERIA: You will be able to use sine and cosine values to work out the height and/or width of a right angled triangle

STARTER: Try these four questions

EQUIPMENT NEEDED: Sharp Pencil, Ruler and Protractor & Calculator

LESSON: INVESTIGATION
Draw a right angled triangle that has an angle of 10° and a hypotenuse length of 10cm. Measure the length and height of the triangle and put the results into a table. Example Notebook File.

Repeat for triangles with 20°, 30°, 40°, 50°, 60°, 70° & 80°. Fill in the length and height for each triangle you draw. Try to be as accurate as you can and give answers to the nearest millimetre.

QUESTIONS:

1. Can you use your table to find the height of a triangle that has an angle of 30° and a hypotenuse length of 50cm
   
2. Can you use your table to find the height of a triangle that has an angle of 50° and a hypotenuse length of 30cm
   
3. Can you use your table to find the height of a triangle that has an angle of 60° and a hypotenuse length of 120cm
   
4. Can you use your table to find the length of a triangle that has an angle of 10° and a hypotenuse length of 5cm
   
5. Can you use your table to find the length of a triangle that has an angle of 80° and a hypotenuse length of 65cm
   
6. Can you use your table to find the height of a triangle that has an angle of 40° and a hypotenuse length of 1cm
   
7. Can you use your table to find the length of a triangle that has an angle of 70° and a hypotenuse length of 235cm
   
8. Can you use your table to find the height of a triangle that has an angle of 25° and a hypotenuse length of 112cm
   

Discussion on Sine and Cosine on Calculator. What it represents. Making sure calculator is set to DEGREES.

Work through Ex 12F on page 278 and Ex 12G on page 281using your calculator.

How to use sine and cosine on calculator to find length and/or height of triangles of any hypotenuse length and any angle

Lots of examples on IWB. Then have a go at the six questions on the IWB

QUESTION / PROBLEM to solve.

If I know the hypotenuse of a triangle is 15cm and its height is 12cm. Can I work out the angle of the triangle and then the length of the triangle.

Give students 5/10 mins to try and solve this problem.

PLENARY: Checking answers throughout the lesson, Quick summary of lesson from students.