`(3)/(4)+(4)/(13)-:(3)/(52)-6`

Show that the three lines with direction cosines quad (12)/(13),(-3)/(13),(-4)/(13),(4)/(13),(12)/(13),(3)/(13);(3)/(13),(-4)/(13),(12)/(13) are mutually perpendicular.

Show that the three lines with direction cosines (12)/(13),(-3)/(13),(-4)/(13);4/(13);(12)/(13),3/(13);3/(13),(-4)/(13),(12)/(13) are mutually perpendicular.

Show that the three lines with direction cosines (12)/(13),(-3)/(13),(-4)/(13),4/(13),(12)/(13),3/(13);3/(13),(-4)/(13),(12)/(13) are mutually perpendicular.

Show that the three lines with direction cosines (12)/(13),(-3)/(13),(-4)/(13);4/(13);(12)/(13),3/(13);3/(13),(-4)/(13),(12)/(13) are mutually perpendicular.

(8)/(4)-(6)/(3)+(9)/(12)-:(15)/(13)

(1.3)/(1!) +(2.4)/(2!)+(3.5)/(3!) + (4.6)/(4!) + .......oo = .......

Divide :(-3)/(4)by-6 (ii) (2)/(3)by(-7)/(12)-4by(-3)/(5) (iv) (-3)/(13)by(-4)/(65)

Show that the lines with direction cosines ((12)/(13),(-3)/(13),(-4)/(13))and((4)/(13),(12)/(13),(3)/(13)) are perpendicular to each other.

Prove that, (1.3)/(1!)+(2.4)/(2!)+(3.5)/(3!)+(4.6)/(4!)+.....=4e