Can someone please help me find the radius im struggling <\3

Consider the proof. given: segment ab is parallel to line de. prove: what is the missing statement in step 5?

17. a researcher measures three variables, x, y, and z for each individual in a sample of n = 20. the pearson correlations for this sample are rxy = 0.6, rxz = 0.4, and ryz = 0.7. a. find the partial correlation between x and y, holding z constant. b. find the partial correlation between x and z, holding y constant. (hint: simply switch the labels for the variables y and z to correspond with the labels in the equation.) gravetter, frederick j. statistics for the behavioral sciences (p. 526). cengage learning. kindle edition.

Simplify. (-2)^-3 a. -8 b. -1/8 c. 1/8 d. 8