If sin x=0.5, what is the value of cos x?

Is the figure congruent? yes or no?

How do i simply this expression (quadratic formula basis) on a ti-84 or normal calculator?

For the chance to be team captain, the numbers 1-30 are put in a hat and you get two chances to pick a number, without replacement. which formula correctly shows how to find the probability that you choose the number 1 and then 2?