Fill in the blanks with the correct rational numbers. Write the answers using no spaces as either integers or fractions in lowest terms, e.g. "3" or "2/7". \cos \left(\theta_{1}\right) \sin

\left(\theta_{2}\right)= \cos \left(\theta_{1}+\theta_{2}\right)+ \cos \left(\theta_{1}-\theta_{2}\right)+ \sin \left(\theta_{1}+\theta_{2}\right)+ \sin \left(\theta_{1}-\theta_{2}\right)