Scientific Calculator

Rather than applying each key immediately like a basic calculator, this tool builds an expression string on the upper display line. Pressing digits, operators, parentheses, constants and functions appends to that expression, and the lower line shows a live evaluation of it as you type, so you can see the running answer before committing. Pressing equals finalises the result and moves the calculation into history.

Operator precedence follows standard mathematical rules: powers and roots bind more tightly than multiplication and division, which in turn bind more tightly than addition and subtraction, and parentheses override everything. This is why 2 plus 3 times 4 evaluates to 14 rather than 20.

The DEG and RAD toggle changes how trigonometric arguments are interpreted. In DEG mode the calculator converts your angle to radians internally before evaluating, since the underlying maths functions work in radians. Inverse trigonometric results are converted back the same way, so arcsine of 0.5 returns 30 in DEG mode and roughly 0.5236 in RAD mode.

The INV toggle swaps the function keys in place: sine becomes arcsine, square root becomes square, log becomes ten to the power x, and natural log becomes the exponential.

Check the mode badge reads DEG. Press 5, then the multiply key, then sin, which inserts the sine function and an opening parenthesis. Type 30 and close the parenthesis. Press plus, then the square root key, type 16 and close.

The expression line reads 5 × sin(30) + √16, and the preview line already shows the answer. Sine of 30 degrees is exactly 0.5, so 5 times 0.5 is 2.5. The square root of 16 is 4. The total is 2.5 plus 4, which is 6.5. Press equals to commit it, and the calculation is added to history as the expression with its result.

Switch the mode to RAD and re-enter the same expression: sine of 30 radians is approximately minus 0.988, so the first term becomes about minus 4.94 and the total drops to roughly minus 0.94. This is the single most common source of wrong trigonometric answers.

For a factorial check, press 5 then the n! key: 5 factorial is 5 times 4 times 3 times 2 times 1, which is 120. Press M+ to add 120 to memory and MR to recall it into a later expression.

Arithmetic uses the browser's double-precision floating point numbers, the same representation as almost every calculator app and spreadsheet. That gives roughly fifteen to sixteen significant digits, and it produces the familiar rounding artefacts: some decimal fractions cannot be stored exactly, so a long chain of operations can end in a trailing digit you did not expect. For everyday and coursework use this is invisible; for exact fractional work, use a symbolic tool instead.

Tangent has no value at 90 degrees and its odd multiples, where the function is undefined. Depending on rounding you may see an extremely large number rather than an error, so treat any implausibly huge tangent result as a sign you are at an asymptote.

Factorials grow faster than any other key on the pad. Beyond about 170 the result exceeds the largest representable number and returns infinity, and non-integer or negative inputs are not valid factorials.

The most frequent mistake is not a calculation error at all: it is leaving the calculator in RAD when the question is in degrees, or the reverse. Check the mode badge on the display before every trigonometric calculation. History lets you restore an earlier expression and re-run it after switching.