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TAN

Supported, behaves as documented

Category: Math and trigonometry · Last tested 2026-09-01

Real compatibility results for the TAN function: executed in Excel for the web, Google Sheets and LibreOffice Calc, with desktop Excel behavior from Microsoft’s official documentation (we do not run desktop Excel — Excel for the web is a different application and is executed separately). Syntax and links to that documentation are below.

Support matrix

EngineDocumentedLive-testedVerdict
Excel (desktop)Yes No — documented only n/a
Excel for the web— Yes (recalc, 2026-09-01) Supported, behaves as documented
Google SheetsYes Yes (Drive import, 2026-08-31) Supported, behaves as documented
LibreOffice CalcYes Yes (25.8.7.3, 2026-08-31) Supported, behaves as documented

LibreOffice version history

We executed the same test cases under each LibreOffice release to show exactly when TAN’s support changed — not documentation claims, real results.

LibreOffice versionVerdictTested
24.2.0.3 Supported, behaves as documented 2026-08-31
24.8.7.2 Supported, behaves as documented 2026-08-31
25.2.0.3 Supported, behaves as documented 2026-08-31
25.8.7.3 Supported, behaves as documented 2026-08-31

Executed test cases

Excel for the web (executed 2026-09-01 via OneDrive recalculation)

These values come from Excel for the web, not from desktop Excel. They are two different implementations of the calculation engine, and this run measured only the web one: the corpus was uploaded to OneDrive as .xlsx, recalculated by Excel for the web on open, and downloaded again for readback. Excel for the web is a rolling service with no pinnable version, so the run is identified by its date. Where a value here disagrees with the Expected column — which is Microsoft’s documentation of the desktop product — we cannot tell you whether the web engine diverges from the desktop one or the documentation is wrong about both, because we do not run desktop Excel.

FormulaDescriptionResultExpectedVerdict
=ROUND(TAN(0.785),5) Microsoft's first documented example, at the five decimals it publishes 0.9992 0.9992
Provenance

Microsoft publishes =TAN(0.785) = 0.99920 ("Tangent of 0.785 radians"). DERIVATION: tan(0.785) = 0.9992039901050426572858 at 50 digits, which is 0.99920 at the published precision -- 0.9992 as a number, the trailing zero being the page's formatting. Microsoft's page was read live on 2026-08-31 at https://support.microsoft.com/en-us/excel/functions/tan-function. FETCH NOTE FOR THIS BATCH: batch F recorded every /en-us/office/<name>-function-<guid> URL returning Microsoft's 'Sorry, the page you're looking for can't be found' body; today BOTH paths serve the article again -- the GUID form redirects to /en-us/excel/functions/<slug>-function -- and every page cited in this batch came back complete (217-223 KB) in one or two attempts, with no 87 KB stub responses. Nothing here is sourced from a search snippet or a mirror.

 Matched
=ROUND(TAN(45*PI()/180),10) Microsoft's second documented row: 45 degrees converted by hand 1 1
Provenance

Microsoft publishes =TAN(45*PI()/180) = 1. tan(pi/4) = 1 exactly in real arithmetic; the ROUND(...,10) wrapper absorbs the double-precision residue from PI()/180 the same way the SIN(PI()) case does.

 Matched
=ROUND(TAN(RADIANS(45)),10) Microsoft's third documented row: the same angle via RADIANS() 1 1
Provenance

Microsoft publishes =TAN(RADIANS(45)) = 1, matching the hand-converted row. Kept separate because it asserts RADIANS() and *PI()/180 agree, which is a different claim from TAN being right.

 Matched
=ROUND(TAN(0.785),10) The first example carried to ten decimals 0.9992039901 0.9992039901
Provenance

Asserted at ten places from the derivation: 0.9992039901. Five published decimals cannot separate tan(0.785) from the nearby exact 1 at tan(pi/4), and pi/4 = 0.7853981634 is only 0.0004 away.

 Matched
=ROUND(TAN(1)-SIN(1)/COS(1),15) tan checked against sin/cos as the engine itself computes them 0 0
Provenance

tan(x) = sin(x)/cos(x) by definition. Asserting the difference is zero makes the engine check TAN against its own SIN and COS, with no constant from us. The TAN page publishes no error-condition remarks at all -- only the degrees-to-radians note -- so no error case is asserted for this function.

 Matched

Google Sheets (executed 2026-08-31 via Drive import)

Google Sheets is a rolling service with no pinnable version, so this run is identified by its date. The corpus was imported to Drive as .xlsx, recalculated by Sheets, and exported back for readback.

FormulaDescriptionResultExpectedVerdict
=ROUND(TAN(0.785),5) Microsoft's first documented example, at the five decimals it publishes 0.9992 0.9992
Provenance

Microsoft publishes =TAN(0.785) = 0.99920 ("Tangent of 0.785 radians"). DERIVATION: tan(0.785) = 0.9992039901050426572858 at 50 digits, which is 0.99920 at the published precision -- 0.9992 as a number, the trailing zero being the page's formatting. Microsoft's page was read live on 2026-08-31 at https://support.microsoft.com/en-us/excel/functions/tan-function. FETCH NOTE FOR THIS BATCH: batch F recorded every /en-us/office/<name>-function-<guid> URL returning Microsoft's 'Sorry, the page you're looking for can't be found' body; today BOTH paths serve the article again -- the GUID form redirects to /en-us/excel/functions/<slug>-function -- and every page cited in this batch came back complete (217-223 KB) in one or two attempts, with no 87 KB stub responses. Nothing here is sourced from a search snippet or a mirror.

 Matched
=ROUND(TAN(45*PI()/180),10) Microsoft's second documented row: 45 degrees converted by hand 1 1
Provenance

Microsoft publishes =TAN(45*PI()/180) = 1. tan(pi/4) = 1 exactly in real arithmetic; the ROUND(...,10) wrapper absorbs the double-precision residue from PI()/180 the same way the SIN(PI()) case does.

 Matched
=ROUND(TAN(RADIANS(45)),10) Microsoft's third documented row: the same angle via RADIANS() 1 1
Provenance

Microsoft publishes =TAN(RADIANS(45)) = 1, matching the hand-converted row. Kept separate because it asserts RADIANS() and *PI()/180 agree, which is a different claim from TAN being right.

 Matched
=ROUND(TAN(0.785),10) The first example carried to ten decimals 0.9992039901 0.9992039901
Provenance

Asserted at ten places from the derivation: 0.9992039901. Five published decimals cannot separate tan(0.785) from the nearby exact 1 at tan(pi/4), and pi/4 = 0.7853981634 is only 0.0004 away.

 Matched
=ROUND(TAN(1)-SIN(1)/COS(1),15) tan checked against sin/cos as the engine itself computes them 0 0
Provenance

tan(x) = sin(x)/cos(x) by definition. Asserting the difference is zero makes the engine check TAN against its own SIN and COS, with no constant from us. The TAN page publishes no error-condition remarks at all -- only the degrees-to-radians note -- so no error case is asserted for this function.

 Matched

LibreOffice Calc 25.8.7.3 (tested 2026-08-31)

FormulaDescriptionResultExpectedVerdict
=ROUND(TAN(0.785),5) Microsoft's first documented example, at the five decimals it publishes 0.9992 0.9992
Provenance

Microsoft publishes =TAN(0.785) = 0.99920 ("Tangent of 0.785 radians"). DERIVATION: tan(0.785) = 0.9992039901050426572858 at 50 digits, which is 0.99920 at the published precision -- 0.9992 as a number, the trailing zero being the page's formatting. Microsoft's page was read live on 2026-08-31 at https://support.microsoft.com/en-us/excel/functions/tan-function. FETCH NOTE FOR THIS BATCH: batch F recorded every /en-us/office/<name>-function-<guid> URL returning Microsoft's 'Sorry, the page you're looking for can't be found' body; today BOTH paths serve the article again -- the GUID form redirects to /en-us/excel/functions/<slug>-function -- and every page cited in this batch came back complete (217-223 KB) in one or two attempts, with no 87 KB stub responses. Nothing here is sourced from a search snippet or a mirror.

 Matched
=ROUND(TAN(45*PI()/180),10) Microsoft's second documented row: 45 degrees converted by hand 1 1
Provenance

Microsoft publishes =TAN(45*PI()/180) = 1. tan(pi/4) = 1 exactly in real arithmetic; the ROUND(...,10) wrapper absorbs the double-precision residue from PI()/180 the same way the SIN(PI()) case does.

 Matched
=ROUND(TAN(RADIANS(45)),10) Microsoft's third documented row: the same angle via RADIANS() 1 1
Provenance

Microsoft publishes =TAN(RADIANS(45)) = 1, matching the hand-converted row. Kept separate because it asserts RADIANS() and *PI()/180 agree, which is a different claim from TAN being right.

 Matched
=ROUND(TAN(0.785),10) The first example carried to ten decimals 0.9992039901 0.9992039901
Provenance

Asserted at ten places from the derivation: 0.9992039901. Five published decimals cannot separate tan(0.785) from the nearby exact 1 at tan(pi/4), and pi/4 = 0.7853981634 is only 0.0004 away.

 Matched
=ROUND(TAN(1)-SIN(1)/COS(1),15) tan checked against sin/cos as the engine itself computes them 0 0
Provenance

tan(x) = sin(x)/cos(x) by definition. Asserting the difference is zero makes the engine check TAN against its own SIN and COS, with no constant from us. The TAN page publishes no error-condition remarks at all -- only the degrees-to-radians note -- so no error case is asserted for this function.

 Matched

Docs & syntax