I have a important question​

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

In a column proof the right column states your reasons

Rachel is studying the population of a particular bird species in a national park. she observes every 10th bird of that species that she can find in the park. her conclusion is that the birds living in the park who belong to that species generally feed on insects. rachel's sample is . based on the sample she picked, rachel's generalization is . reset next