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In the diagram shown, <b and <c are complementary, as are <e and <f. Angles <b and <d and supplementary. Because of alternative angles of parallel lines, <b = <b', and <d = <d', assuming lines Y and Z are parallel. From vertical angles theorem, <b = <b.
Length of a vector can be written as ||v|| (the "norm" of vector v)
Distance between two points = √(Δx² + Δy²) (based on Pythagorean theorem)
Distance of two vectors: first add the vectors to make a combined vector Adding vectors: add each part of the vector, ie. (x1 + x2, y1 + y2)