Answer:
see explanation
Step-by-step explanation:
The difference identity for the product is
sinxsiny = [tex]\frac{1}{2}[/tex] [ cos(x - y) - cos(x + y) ], thus
sin20sin10
= [tex]\frac{1}{2}[/tex] [ cos(20 - 10) - cos(20 + 10) ]
= [tex]\frac{1}{2}[/tex] ( cos10 - cos30 )
