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cis (mathematics)
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<p> cis is a <a href="/facts/Mathematical_notation/vHgEE8cE">mathematical notation</a> defined by cis <i>x</i> = cos <i>x</i> + <i>i</i> sin <i>x</i>, where cos is the <a href="/facts/Cosine/czej7ur0">cosine</a> function, i is the <a href="/facts/Imaginary_unit/1SCllQlU">imaginary unit</a> and sin is the <a href="/facts/Sine/gQ6LXK8z">sine</a> function. x is the <a href="/facts/Argument_(complex_analysis)/JSjfxb5U">argument</a> of the complex number (angle between line to point and x-axis in <a href="/facts/Polar_form/2w7mqI7e">polar form</a>). The notation is less commonly used in mathematics than <a href="/facts/Euler%2527s_formula/Wq7VXIV0">Euler's formula</a>, <i>eix</i>, which offers an even shorter notation for cos <i>x</i> + <i>i</i> sin <i>x</i>, but cis(x) is widely used as a name for this function in <a href="/facts/Library_(computing)/xRzL3P7q">software libraries</a>. </p>