f.4 mathz.

1. let x,y,and z are interior angles in a triangle. express tan[(y+z)/2] in terms of x

2. assume z varies directly as x and inversely as the square root of y . when x=2, x:y:z=1:2:3. find the value of z when x:y:z=3:4:5

3. assume y partly varies directly as x and partly varies directly as x^2. when x=-1, y=2. when x=2, y= -10. if x is an integer and y>0, find all the possible values of x