Trigonometry: Choosing the Right Formula for Triangles
Right-angled triangles are your best mates in trigonometry because they follow clear, predictable rules. The key is knowing which formula to grab depending on what information you've got and what you're trying to find.
For finding missing sides when you know two other sides, Pythagoras' theorem is your go-to: aยฒ + bยฒ = cยฒ. Remember, 'c' is always the hypotenuse - that's the longest side opposite the right angle. In the example shown, 4ยฒ + 3ยฒ = cยฒ, which gives us 16 + 9 = 25, so c = 5.
When you need to find sides or angles and you know some angle measurements, SOH CAH TOA comes to the rescue. Sin uses opposite over hypotenuse, cos uses adjacent over hypotenuse, and tan uses opposite over adjacent.
Non right-angled triangles need different tools entirely. You'll use the sine rule a/sin(A)=b/sin(B)=c/sin(C) or the cosine rule a2=b2+c2โ2bccos(A) depending on what information you're given. Don't worry about memorising when to use which - your exam questions will usually give you hints about which formula fits best.
Quick tip: Always sketch your triangle and label what you know - it makes choosing the right formula much easier!