Using the Sine, Cosine and Tangent Rules Objective: To relate the sine, cosine and tangent functions with the sides of a triangle to create rules. Use the rules to calculate the missing side length of a triangle.

RECAP Task  Independent effort  No communication  Reading Time: 3 minutes  Writing: 2 minutes

TASK: (2 mins). Talk to the person ‘adjacent’ to you about the information below…. Use Pythagoras Theorem to calculate the missing side length, x. Will this method work??? Explain why or why not.

Objective of today’s class  Today, we will relate the sine, cosine and tangent to the O,A and H sides of the triangle and create 3 rules.  We will use these 3 rules to calculate the missing side length in a right-angled triangle.

Sine Rule (SOH)

Cosine Rule (CAH)

Tangent Rule (TOA)

An easy way to remember:  SOH CAH TOA  Simply tells you the 2 sides and the function

How do we write the rules?  EXAMPLE  For the triangle below, write the Sine rule (Label as O A H first) Answer

You Tube video Finding the side length using Sine, Cos and Tangent Finding the side length using Sine, Cos and Tangent 

Complete Worksheet 2

EXAMPLE: Use the rules to calculate the missing side length, x.  Label the sides as O, A and H  List the information given  Select the rule that uses the information listed.  Replace with numbers and solve.

Work Set  Complete worksheet 3