The use of Double-Angle formulas help reduce the degree of difficulty. Sin 2a 2 sin a cos a. In this section you will learn formulas that establish a relationship between the basic trigonometric values sin cos tan for a particular angle and the trigonometric values for an angle that is either double- or half- of the first angle.
Trigonometric Double-Angle and Half-Angle Formulas Written by tutor Michael B.
We will use this to obtain the sine of a double angle. A sin 2th 2 sin th cos th. Cosine Double Angle Identity Whats so cool about these identities is that throughout our journey of proving fundamental identities we can begin to see how one function can be easily expressed as a sum or difference or multiple of another. This unit looks at trigonometric formulae known as the doubleangleformulae.