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GeoGebraGeoGebra Classroom

Parallel Lines - Co-interior Angles

Blue parallel lines cut across by a red transversal
The diagram shows a pair of co-interior angles (p and v). Move points B and C to make v take a range of values and see how p is affected. For example, make v = 100º, 110º, 120º, 130º and 140º and note the size of p in each case. There are two pairs of co-interior angles - click the check box to look at the other pair (q and w). Move points B and C to a variety of positions and note how q and w relate to each other. So what have you deduced about co-interior angles?