Help with this thank you

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

Write two point-slope equations for the line passing through the points (6, 5) and (3, 1)

If the endpoints of the diameter of a circle are (8, 6) and (2,0), what is the standard form equation of the circle? a) (x + 5)2 + (y + 3)2 = 18 (x + 5)2 + (y + 3)2 = 3.72 (x - 5)2 + (y - 3)2 = 18 d) (x - 5)2 + (y - 3)2 = 32