SOHCAHTOA discovery lesson

A complete lesson for first introducing how to find angles in a right-angled triangle using a trig ratio, but as a pupil-led investigation. Intended to come after pupils have practiced identifying hypotenuse/opposite/adjacent and calculating sin/cos/tan.

Activities included:

Starter:
A set of questions to check pupils can correctly calculate sin, cos and tan from a triangle’s dimensions.

Main:
A structured investigation where pupils:

1. Investigate sin, cos and tan for triangles of different size but the same angles (i.e. similar triangles), by measuring dimensions of triangles and calculating ratios
2. Investigate what happens as the angle varies by measuring dimensions of triangles, calculating ratios, and plotting separate graphs of sin, cos and tan.
3. Using their graphs to estimate angles for conventional SOHCAHTOA questions (i.e. finding an angle given two sides)

Plenary:
A prompt to get pupils to discuss/reflect on their understanding of the use of trig ratios.

Printable worksheets and answers included.

Please review if you buy as any feedback is appreciated!