Basically degrees of freedom are related to sample size (n-1). If the df increases, it also stands that the sample size is increasing; the graph of the t-distribution will have skinnier tails, pushing the critical value towards the mean.
Line segments are parts of line that have fixed ends. For them to be perpendicular, the angle between them should be 90°. Bisecting lines are those that cut each other into two equal parts. If the lines intersect but the conditions above are not satisfied then, the lines are non-perpendicular and non-bisecting, intersecting lines.
