👉 Learn how to evaluate the cosine of an angle in radians using the sum/difference formulas. To do this, we first express the given angle as a sum or a difference of two (easy to evaluate) angles, ...

Learn how to evaluate the double angle of sine. The value of the sine of double a given angle can be obtained given the value of the sine of the angle. The value of the sine of double a given angle is ...

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.