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Old 07-25-2007   #5
dylan k
Posts: n/a

you don't show what angles correspond to angle 4 or 5, but there's a simple way to find the answer:AB means line AB, ie, a line that PASSES THROUGH point A and B. the same with line CD.when two lines are parallel, it means that they will never intersect each other, even if each line was infinitely long. Mathematically what this means is that lines AB and CD have the same slope. Do you know how to calculate the slope of each line? each point has an X and a Y number, ieA = (Ax,Ay) whereAx = x-coordinateAy = Y coordinateto calculate the slope, compute:slope = rise/run = (By-Ay)/(Bx-Ax)slope(of line CD) = (Dy-Cy)/(Dx-Cx)if these two numbers are the same, the lines are parallel