Trigonometry - SOHCAHTOA finding sides

A complete lesson on using sin, cos and tan to find an unknown side of a right-angled triangle. Designed to come after pupils have been introduced to the trig ratios, and used them to find angles in right-angled triangles. Please see my other resources for complete lessons on these topics.

Activities included:

Starter:
A quick reminder and some questions about using formulae triangles (e.g. the speed, distance, time triangle). This is to help pupils to transfer the same idea to the SOHCAHTOA formulae triangles.

Main:

• A few examples and questions for pupils to try, on finding a side given one side and an angle. Initially, this is done without reference to SOHCAHTOA or formulae triangles, so that pupils need to think about whether to multiply or divide.
• More examples, but this time using formulae triangles.
• A worksheet with a progression in difficulty, building up to some challenging questions on finding perimeters of right-angled triangles, given one side and an angle.
• A tough extension, where pupils try to find lengths for the sides of a triangle with a given angle, so that it is has a perimeter of 20cm.

Plenary:
A prompt to get pupils thinking about how they are going to remember the rules and methods for this topic.

Printable worksheets and answers included.

Please review if you buy as any feedback is appreciated!

Error on previous version now fixed. If you have bought this already and want the amended version, please message me and I will email the file directly.