In a right triangle abc, tan(a)= 20/21.find sin(a) and cos(a)

Sin(a)=opposite/hypotenuse
        ∴hypotenuse=√20²+21² 
                             =√400+441
                             =√841
                             =29
          ∴sin(a)=20/29
                     =0.6897

cos(a)=adjascent/hypotenuse
           =21/29
           =0.7241 

The sun's parallax would be 180 degrees, greater than which you can't get.  so a. would be your anwser