How did my geometry teacher go from cos^-1 to cos?

Solve the equation - 2(m -30) = -6m a-15 b-13 c-8 d8

Consider a bag that contains 220 coins of which 6 are rare indian pennies. for the given pair of events a and b, complete parts (a) and (b) below. a: when one of the 220 coins is randomly selected, it is one of the 6 indian pennies. b: when another one of the 220 coins is randomly selected (with replacement), it is also one of the 6 indian pennies. a. determine whether events a and b are independent or dependent. b. find p(a and b), the probability that events a and b both occur.

What is the distance from zero if a quadratic function has a line of symmetry at x=-3 and a zero at 4