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In graph a, for t equals 0, the x axis displays the values from 0 to start fraction 3 lambda over 2 end fraction, and the y axis displays the values from negative A to A. The sinusoidal wave starts from (0, A), and passes through (start fraction lambda over 4 end fraction, 0), (start fraction lambda over 2 end fraction, negative A), (lambda, A), (start fraction 5 lambda over 4 end fraction, 0), (start fraction 3 lambda over 2 end fraction, negative A). The distance from start fraction lambda over 2 end fraction to start fraction 3 lambda over 2 end fraction is labeled lambda.