## anonymous 5 years ago Use identities (no calculators) to find the exact value for (sin 15)(cos 45) + (cos 15)(sin 45).

1. anonymous

This is the 'addition angle formula $sin(a+b)=sin(a)cos(b)+cos(a)sin(b)$

2. anonymous

here $a=15, b=45$ so the left hand side is $sin(15+45)=sin(60)$

3. anonymous

$sin(60)=\frac{\sqrt{3}}{2}$

4. anonymous

Thanks! What if they are angles such as Use identities (no calculators) to find the exact value for (sin 38)(sin 112) -( cos 38)(cos 112) ???