Please help ill give extra points

Which expression is equivalent to 5r6141 2r+st6

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

Will mark determine whether the conjecture is true or false. give a counterexample for any false conjecture. given: points r, s, and t conjecture: r, s, and t are coplanar. a) false; the points do not have to be in a straight line. b) true c) false; the points to not have to form right angles. d) false; one point may not be between the other two.