7*√33*sin(arccos 4/7)
1)sin(arccos(4/7))
sin(arcsin(4/7))=4/7
cos^2A=1-sin^2A
cos^2(4/7)=1-(4/7)^2=33/49
cos(4/7)=sqrt(33)/7
sin(arccos(4/7))= sqrt(33)/7
2)7*√33*sqrt(33)/7=33