If angle of inclination of lines l1 and l2 are 60 degree and 135 degree respectively the tangent of the angle between the lines measured from l2 to l1 is given by

Answer 1

that would be
tan(135-60) = (tan135-tan60)/(1 + tan35 tan60)
= (-1 - √3)/(1 - √3)
= 2+√3