What is the exact value of cos (-pi/2)

Rose drew a regression line for this paired data set. her line passed through (1, 2) and (3, 5) . what is the equation of rose's regression line?

What is the difference between regular convex and concave polygons

Mrs. morton has a special reward system for her class. when all her students behave well, she rewards them by putting 3 marbles into a marble jar. when the jar has 100 or more marbles, the students have a party. right now, the the jar has 24 marbles. how could mrs. morton reward the class in order for the students to have a party?