d_{HD}&= \sqrt{\left(x_2-x_1 \right)^2+ \left(y_2-y_1 \right)^2} && d_{H^\prime D^\prime}= \sqrt{\left(x_2-x_1 \right)^2+ \left(y_2-y_1 \right)^2} \\d_{HD}&= \sqrt{\left(1-3.5 \right)^2+ \left(3-1 \right)^2} && d_{H^\prime D^\prime}= \sqrt{\left(-6- \left(-3.5 \right) \right)^2+ \left(4-2 \right)^2} \\d_{HD}&= \sqrt{\left(-2.5 \right)^2+ \left(2 \right)^2} && d_{H^\prime D^\prime}= \sqrt{\left(-2.5 \right)^2+ \left(2 \right)^2} \\d_{HD}&= \sqrt{6.25+4} && d_{H^\prime D^\prime}= \sqrt{6.25+4} \\d_{HD}&= \sqrt{10.25} && d_{H^\prime D^\prime}= \sqrt{10.25} \\d_{HD}&=3.20 \ cm && d_{H^\prime D^\prime}=3.20 \ cm
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