An expression is defined as a set of numbers, variables, and mathematical operations. Using a cosine function identity cos(120° − (30° + a)) can be written as sin a.
What is an Expression?
In mathematics, an expression is defined as a set of numbers, variables, and mathematical operations formed according to rules dependent on the context.
The given cosine expression can be rewritten as,
cos(120° − (30° + a))
Opening the bracket, to simplify the angle,
= cos(120° − 30° − a)
= cos(90° − a)
Since the cosine and sine angles are complementary to each other, therefore, cos(90° − x) = sin(x), thus, we can write the expression as,
