In right triangle DEF, DE = 9. Find DF.
60°
30°

What is the answer

Which number completes the system of linear inequalities represented by the graph? y> 2x – 2 and x + 4y 2 et 2 3 4

Find the domain of the following expression: 1/(√x)-2

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) = .