How do u find half of a circle

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

Both the red and blue line segments stretch from the center of the circle to a point on the circle. the length of the blue segment is 5. how long is the red line segment?

On a piece of paper, graph y< x+1. then determine which answer matches the graph you drew.