Area of a triangle trigonometry version

A complete lesson on the 1/2 absinC area rule. Doesn’t include ‘reverse’ problems (I’ve made a separate resource on this).

Activities included:

Starter:
A set of questions on area of triangles using bh/2.

Main:

• An area question for pupils to attempt, given two sides and the angle between them. If they spot that they can use SOH to get the perpendicular height, they have effectively ‘discovered’ the 1/2absinC rule. If they don’t spot it, then the rule can be easily explained at this point.
• A set of questions designed to be done as a class using mini whiteboards, progressing from identifying the correct information needed to calculate area, to standard questions, to trickier questions (see cover slide for an example).
• A two-page worksheet (I’d shrink and print as one page) with a similar progression in difficulty, for pupils to consolidate. Includes a suggested extension task in the comments box of the powerpoint.

Plenary:
A closer look at question one from the worksheet, which links to the graph of sine.