Can some one please help me understand this.

Express the following as a function of a single angle, cos(60) cos(-20) - sin(60) sin(-20)

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.

A. what is the area of the base? use complete sentences to explain your reasoning. b. what is the volume of the prism? use complete sentences to explain your reasoning.