If cos a=0•8,what is the value of tan a​

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

Ineed i been stuck on this question since yesterday

Mr. brettler is hanging up a 5-foot tall rectangular welcome sign in the gym. he has drawn a sketch on a coordinate grid. he has the lower vertices of the sign at (9, –3) and (–6, –3). where would the upper vertices be on the grid?