Radians

Angles can be measured in either radians or degrees where 180° = π radians. If you know that 180° = π radians, you can easily convert between the two.

To convert any given angle from the measure of degrees to radians, **the value has to be multiplied by π/180**.

So 30° converts to radians as follows:

30π /180 = π/6 radians

To convert from radians to degrees, you simply have to **multiply the radian value by 180/π**.

To convert π/4 radians into degrees:

180/4 = 45°

Sin, Tan and Cos

All, Sin, Tan and Cos:

This is an All, Sin, Tan and Cos diagram. This determines whether the outcome of the equation will be positive or negative.

Compound Angle formula:

The compound angle (or addition) formulae are:

This is commonly seen in a question where you will be asked to give an expansion of Sin or Cos.

You will need to know your exact values to figure these out.

**Example:**

By writing *75°=45°+30°* determine the exact value of *sin 75°*

sin75°=sin(45+30)°

using the formula for sin(A+B)

= sin45°cos30° + cos45°sin30°

using exact values that you should know

**Double Angle Formula:**

The double angle formulae are

Work hard for your IBDP Mathematics examination!