There are two versions of the cosine rule: Find an unknown side using 𝑎² = 𝑏² + 𝑐² – 2𝑏𝑐 cos𝐴 Find an unknown angle using cos𝐴 = \(\frac{𝑏² + 𝑐² – 𝑎²}{2𝑏𝑐}\) Scientific calculators need to ...

👉 Learn how to evaluate the cosine of an angle in radians using the sum/difference formulas. To do this, we first express ...

👉 Learn how to evaluate the Sine of an angle using the half-angle formula. The half-angle formula for Sine is helpful when you need to determine the exact value of function given an angle but cannot ...

Being able to identify which formula to use, sine or cosine, and when, is necessary to answer questions on this topic successfully. Check you are confident in how to use the sine and cosine rules.