Live DEG/RAD mode strip and dual-mode trig mirror - so the same expression never pretends degrees and radians are interchangeable.
Educational expression pad. DEG ≠ RAD for trig. Not a CAS, graphing suite, or exam memory dump.
By Ahmet C. Toplutaş·Site owner & editor · Math tools
Last updated May 21, 2026 · Reviewed May 21, 2026 · Planning estimates only - not tax, medical, or investment advice
01
A scientific keypad looks like “more buttons than a four-function.” The silent failure mode is not missing a √ key - it is treating degrees and radians as the same dial. Type sin(30) with the wrong angle unit and you still get a confident decimal. Homework keys, CAD scripts, and exam sheets all punish that confidence.
Degrees partition a full turn into 360 parts; radians measure arc length over radius, so a half-turn is π ≈ 3.14159. Classroom geometry almost always wants DEG. Calculus, Fourier work, and most programming libraries default to RAD. Neither is “more correct” - they are different rulers for the same circle.
This page’s framing is DEG ≠ RAD. The panel keeps the active mode visible, evaluates live, and - when trig appears - mirrors the same expression under both conventions so “I got a number” is not mistaken for “I used the intended unit.”
Engineers paste formulas from papers that assume radians; teachers grade worksheets that assume degrees. The keypad does not know your source. Naming the unit first is the literacy skill; pressing sin is secondary.
Decision framing: “Which angle unit is this expression written in?” - not “which function button is closest to my homework verb?”
02
Before digits, set DEG or RAD on the mode strip. Every trig and inverse-trig call reads that strip. Non-trig work (logs, powers, arithmetic) is unchanged by the strip - which is why a mixed homework set can hide a mode error until the first sin/cos line.
Presets jump you into the classic traps: sin(30) under DEG (≈ 0.5), cos(90) under DEG (≈ 0), and sin(pi/2) under RAD (≈ 1). Each preset also stamps the mode it expects, so you practice flipping the strip deliberately instead of hoping the default matches your worksheet.
The expression tape stamps DEG or RAD on every committed line. That stamp is the audit trail when you scroll back and wonder why yesterday’s sin(30) suddenly looks wrong after you switched modes for a calculus problem.
Share links carry both the expression and the mode, so a classmate opens the same unit switch you used - not a blank pad that silently defaults to whatever they last touched.
03
Scientific keys do not suspend arithmetic grammar. Parentheses first, then exponents (^, right-associative so 2^3^2 = 2^(3^2) = 512), then multiplication and division left-to-right, then addition and subtraction. Functions bind to their parenthesized argument: sin(30)^2 squares the sine, while sin(30^2) sines nine hundred.
Implicit multiplication is allowed for readable forms like 2pi and 2(3+1). Prefer explicit * when an expression is getting dense - clarity beats clever notation when you are sharing a link.
Live evaluation updates as you type; = commits the current line to the expression tape and replaces the input with the result so you can chain (Ans-style) without a separate memory register. If the expression is invalid, the verdict shows the error instead of a fake zero.
04
Forward functions sin, cos, tan interpret the argument in the active mode. Inverse functions asin, acos, atan return an angle in that same mode. If you take asin(0.5) in DEG you should see 30; in RAD you should see π/6 ≈ 0.5236.
Domain checks still apply: asin and acos only accept arguments in [−1, 1]. Tan near odd multiples of 90° (DEG) or π/2 (RAD) grows without bound - a huge magnitude is often a mode or parentheses issue, not a deeper mystery.
Inverse results are still angles: if you need a degree measure for a diagram, stay in DEG for the whole asin/acos/atan chain instead of converting by hand after a RAD result.
Triangle solving that needs SSA literacy belongs on the triangle calculator. This page evaluates expressions; that page completes geometric givens - including when SSA ≠ unique.
05
Calculator convention on this keypad: log is common log (base 10); ln is natural log. log(1000) = 3 and ln(e) = 1 are the sanity checks. sqrt, abs, and exp behave as usual; arguments must respect domain (positive for real logs, non-negative for real square roots).
Constants pi and e insert as full-precision values. Scientific notation in literals (1.2e3) is accepted. For converting display forms of large or tiny numbers into normalized scientific notation strings, use the scientific notation converter.
06
When the expression contains trig (or inverse trig), the panel shows two result cards: the value under DEG and the value under RAD. Your active mode is highlighted; tapping the other card switches the strip. That mirror is the unique affordance - a mode literacy check, not a second geometric twin the way ambiguous SSA produces two triangles.
Non-trig expressions hide the mirror on purpose. Showing two identical numbers would train a false habit: “there are always two answers.” DEG ≠ RAD only bites when an angle unit is in play.
Mentally: the mirror is a unit converter for the angle argument, applied automatically whenever trig is detected. It will not rescue a wrong formula or a missing parenthesis - it only answers “did I use the angle ruler my problem assumed?”
Try the sin(30) trap preset: DEG ≈ 0.5, RAD ≈ −0.988. Same keystrokes; different ruler.
07
Example A · Classroom sine. Preset sin(30) in DEG. Confirm ≈ 0.5, then glance at the RAD mirror so you recognize the wrong mode’s fingerprint next time.
Example B · Cosine zero. Preset cos(90) in DEG. Expect ≈ 0. If you see a mid-range decimal, your strip is almost certainly in RAD.
Example C · Radian half-turn partner. Preset sin(pi/2) in RAD. Expect ≈ 1. Typing sin(90) while still in RAD is the inverse trap of Example A.
Example D · Common log. Preset log(1000). Mode strip is irrelevant here; result should be 3. Use this as a control when you suspect the evaluator, not the angle unit.
After presets, type one line from your own homework, commit it with = so the tape stamps the mode, then share the link only when the expression and mode are the ones you mean to send.
If you tutor or grade, send the Share link with mode embedded. The recipient opens the same DEG/RAD setting you used, which removes the “it worked on my calculator” deadlock that is almost always a silent mode mismatch.
08
Most “broken scientific calculator” reports are mode, parentheses, or log-base mismatches - not missing floating-point magic.
sin(30).log is natural log - here log is base 10; use ln for natural.sin(30)^2 vs sin(30^2).sin(pi/2) in DEG is not 1.x or plot graphs.09
Share links are intentional snapshots. Live typing never rewrites the address bar, so a half-edited expression does not leak into a bookmarked URL.
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Stop here for expression evaluation, angle-mode literacy, and quick trig/log checks. Hand off for geometric triangle completion, percentage sentence jobs, or notation formatting of large magnitudes.
11
Trig functions need an angle unit. DEG treats inputs like 30 and 90 as degrees; RAD treats them as radians (about 57.3° per radian). The same typed expression - for example sin(30) - returns different numbers under the two modes. This page’s framing is DEG ≠ RAD so that mode mistake is visible, not silent.
When your expression uses sin, cos, tan, or an inverse trig function, the panel evaluates it in both DEG and RAD and shows both results. Your active mode is highlighted; the other mode is the “what if I had the wrong switch?” check - different from triangle SSA twins, which are two geometric solutions of one given set.
On this calculator, log means log base 10 (common log). Use ln for the natural logarithm. That matches most handheld scientific keypads.
Yes for parentheses, exponents (^, right-associative), then ×÷, then +−. Functions bind tightly: sin(30)^2 means (sin(30))^2 after the argument is closed. Use parentheses when you mean sin of a squared quantity.
sin, cos, tan, asin, acos, atan (mode-aware), ln, log (base 10), sqrt, abs, exp, constants pi and e, and the operators + − × ÷ ^ with parentheses. Scientific notation like 1.2e3 is accepted in numbers.
No. Expression and mode hydrate from the URL on load; the address bar updates only when you use Share or Copy.
Angle mode · DEG ≠ RAD
sin(30) · DEG
0.5
Active mode DEG. Mirror below shows the other convention.
Dual-mode mirror
Same expression, two angle conventions. Active DEG ≈ 0.5; RAD ≈ -0.9880316241. DEG ≠ RAD is a mode literacy check - not two different triangles.
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