Scientific calculator

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and keys / Explicit arithmetic grammar</div><h1>Scientific calculator</h1></header>
<section class="calculator"><div class="result"><span class="eyebrow" id="modeTag">DEG / approximate numeric result</span><div id="answer" class="big">≈14</div><div id="interpretation" class="record">(2 + (3 × 4))</div><p class="caption">Type an expression or use the keys, then calculate.</p></div><form id="form" class="panel below" novalidate><label for="expression">Expression (maximum 100 characters)</label><input id="expression" value="2+3*4" maxlength="100" autocomplete="off" spellcheck="false" class="readout"><div class="row"><div><label for="angle">Trigonometric angle mode</label><select id="angle"><option value="DEG">Degrees (DEG)</option><option value="RAD">Radians (RAD)</option></select></div><div class="buttons"><button class="primary">Calculate =</button><button id="clear" type="button">Clear</button><button id="back" type="button" aria-label="Backspace at the expression cursor">⌫</button></div></div><p id="feedback" class="error" role="status"></p><div class="keypad" id="keypad" role="group" aria-label="Expression insertion keys"></div></form></section>
<section class="panel below"><h2>Expression record</h2><div id="record" class="record"></div><p>Use explicit multiplication: <code>2*pi</code>, not <code>2pi</code>. Functions take one parenthesized argument: <code>sin(30)</code>, <code>sqrt(9)</code>, <code>ln(e)</code> and <code>log(100)</code> (base 10). Powers associate to the right; <code>-2^2 = -4</code>, <code>2^-2 = 0.25</code>.</p><p class="muted">Leading-digit decimal literals only; no exponent notation, variables, assignment, implicit multiplication or complex results. Maximum expression length 100 and recursive nesting 20. The display uses 12 significant digits; intermediate arithmetic uses JavaScript finite numbers. Division by zero, invalid real domains, 0^0 and tan at a singularity are rejected. No graphing, symbolic algebra, exam authorization or persistent memory is provided.</p><div class="sourceLinks"><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math">Numeric function reference</a><a href="https://tms.cs.ny.gov/ExamTutorial/Files/ScientificCaluclatorGuideForOnlineExams.pdf">Function-key hierarchy reference</a></div></section><footer class="below muted">Local working example. Edits last only while this page is open.</footer></main><script data-app>
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