Ineed some with this math question

Express the following as a function of a single angle, cos(60) cos(-20) - sin(60) sin(-20)

All per-unit concepts rely on ratios,meaning,to provide a type of measurement

The birth weights of newborn babies in the unites states follow in a normal distrubution with a mean of 3.4 kg and standard deviation of 0.6 kg. reaserches interested in studying how. children gain weights decide to take random samples of 100 newborn babies and calculate the sample mean birth weights for each sample