What equals 42 & 50 in multiplication so !

What is the first step of an indirect proof of a number that is divisible by two

If the value of cos330°is√3/2 then find cos 165°.

Set $r$ is a set of rectangles such that (1) only the grid points shown here are used as vertices, (2) all sides are vertical or horizontal and (3) no two rectangles in the set are congruent. if $r$ contains the maximum possible number of rectangles given these conditions, what fraction of the rectangles in set $r$ are squares? express your answer as a common fraction.