Answer:
sin a
Step-by-step explanation:
let the unknown term be x.
[tex]x.cos \: b = \frac{1}{2}(sin(a + b) + sin(a - b)) \\ or \: x = \frac{ \frac{1}{2} 2sinacosb}{cosb} \\ or \: x = sin \: a[/tex]
you have to remember that:
2sinAcosB=sin(A+B)+sin(A-B)
