A. How many groups of 6 erasers can be formed from the 18 erasers? Explain.
b. In how many ways can 3 aliens be selected? Explain.
c. In how many ways can 3 aliens and 3 flying saucers be selected? Explain.
d. What is the probability that 3 aliens and 3 flying saucers will be selected? Explain.
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For what is the measure of the angle at the top of the shed? a. multiplication of areas b. squaring of areas c. addition of areas d. division of areas

What is the first quartile of the data set? 10, 11, 12, 15, 17, 19, 22, 24, 29, 33, 38 a. 12 b. 19 c. 29 d. 10

Prove (a) cosh2(x) − sinh2(x) = 1 and (b) 1 − tanh 2(x) = sech 2(x). solution (a) cosh2(x) − sinh2(x) = ex + e−x 2 2 − 2 = e2x + 2 + e−2x 4 − = 4 = . (b) we start with the identity proved in part (a): cosh2(x) − sinh2(x) = 1. if we divide both sides by cosh2(x), we get 1 − sinh2(x) cosh2(x) = 1 or 1 − tanh 2(x) = .