Question

options for drop down are:1. use the quotient identities2. use the even-odd identities3. factor4. clear the parenthesis

Answer 1

Step 1:

Write the expression

cos( x + y ) - cos ( x - y)

Step 2

Apply the multiply angle theorem

cos(a + b) = cosacosb - sinasinb

cos(a - b) = cosacosb + sinasinb

Step 3

`\begin{gathered} \cos (x\text{ + y) = cosxcosy - sinxsiny} \\ \cos (x\text{ - y) = cosxcosy + sinxsiny} \end{gathered}`

Step 4: