`(sqrt(24))/(8)+(sqrt(54))/(9)`

If the angle between the lines whose direcrtion cosines are (-(2)/(sqrt(21)),(C)/(sqrt(21)),(1)/(sqrt(21)))and((3)/(sqrt(54)),(3)/(sqrt(54)),(-6)/(sqrt(54))) is (pi)/(2) , then the value of C is

If the angle betweenthe lines whose direction cosines are (-(2)/(sqrt(21)), (C )/(sqrt(21)), (1)/(sqrt(21))) and ((3)/(sqrt(54)), (3)/(sqrt(54)), -(6)/(sqrt(54))) is (pi)/(2) , then the value of C is

Simplify the following (i) sqrt45-3sqrt20+4sqrt5 (ii) sqrt(24)/8 + sqrt54/9 (iii) root4(12) xx root7(6) (iv) 4sqrt28 div 3sqrt7 div root3(7) (v) 3sqrt3+2sqrt27 + 7/(sqrt3) (vi) (sqrt3-sqrt2)^(2) (vii) root4(81)-8root3(216)+15root5(32)+ sqrt225 (viii) 3/sqrt8+ 1 / sqrt2 (ix) (2sqrt3)/3- (sqrt3)/6

If x=(2sqrt(24))/(sqrt(3)+sqrt(2)) then the value of (x+sqrt(8))/(x-sqrt(8))+(x+sqrt(2))/(x-sqrt(2)) is