Tues May 1st – Finding an angle using the Cosine Rule, Area of a triangle

LEARNING OBJECTIVE: Discover how to use the cosine rule to find a missing angle

SUCCESS CRITERIA: You will be able to use the cosine rule to find the missing angle in a triangle

HINT: You have to use the re-arranged cosine rule to find the missing angle when you have all three sides of the triangle and NONE of the angles

STARTER: SOLVE THIS PROBLEM

The hour hand of a clock is 6.2 cm long, the minute hand is 4.5 cm long.

What is the distance between the ends of the hands at exactly 7 o'clock

LESSON: Use above example to revise using cosine rule to find a length then work through this lesson to look at using a re-arranged version of the cosine rule to find out an angle of a triangle when you know all three lengths but none of the angles.

Now have a go at Q2 page 488, then q6 onwards on page 488

In last 15 mins briefly look at formula for area of a triangle using this lesson Screen 4 onwards.

PLENARY: Checking answers, checking confidence of students on Sine Rule, Cosine Rule and Area of a triangle Rule