Tues Feb 28th – Intro to Trigonometry (continued)

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

Example Notebook File.

STARTER: Use the Measurements in this Table which are for the length and width of triangles with a Hypotenuse of 100mm

Angle	Length	Height
0°	100mm	0mm
10°	98mm	17mm
20°	94mm	34mm
30°	87mm	50mm
40°	77mm	64mm
50°	64mm	77mm
60°	50mm	87mm
70°	34mm	94mm
80°	17mm	98mm
90°	0mm	100mm

 

Can you answer these questions

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
   

LESSON:

CAN we use the table to the length of a small triangle that has a 1mm hypotenuse?

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

Look at sin(10°), compare with table

Look at cos(50°). Compare with table

 

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

Discussion on any findings

 

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.