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
[tex]\begin{gathered} \cos (x\text{ + y) = cosxcosy - sinxsiny} \\ \cos (x\text{ - y) = cosxcosy + sinxsiny} \end{gathered}[/tex]
Step 4:
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