Which line plot (s) represents 2/4?

Which is an equation for the nth terms of the sequence 12,15,18,21

Astick 2 m long is placed vertically at point b. the top of the stick is in line with the top of a tree as seen from point a, which is 3 m from the stick and 30 m from the tree. how tall is the tree?

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