Mr. Duc asked Perry to set up 450 chairs in a large hall. Perry puts 20 chairs in each row. He has already set up 15 rows of chairs. How many more chairs must he set up

Use the given information to determine the exact trig value. cot theta = -square root of 5 / 2 , pi/2 < theta < pi, tan theta a.) - square root of 5 / 5 c.) - 2 square root of 5 / 5 b.) - square root of 5 / 2 d.) the answer isn't d, it was incorrect