MyTrigCalculator.com

Corrections & Changelog

We publish the errors we find. If a calculator on this site ever gave you a wrong answer, you deserve to know what it was and when it was fixed. Our checking process is described on the methodology page, and you can report a problem here.

A full audit of every calculator, diagram and worked example. We recomputed each result by hand, fixed what was wrong, and added an automated test for every fix.

Corrections

  • Isosceles Triangle: Sine and cosine were swapped in five of the seven input combinations, giving wrong angles, base or height (equal sides 10 and base 10 returned 30°/30°/120° instead of 60°/60°/60°). The same error appeared in a formula and an FAQ answer on the page. All corrected.
  • Triangle Solver: In SAS mode an obtuse angle was reported as its supplement (a = 10, b = 3, C = 20° gave A = 28.13° instead of 151.87°). The solver now uses the Law of Cosines for that angle. Angle arcs in the method diagrams were drawn outside the triangle.
  • Law of Sines: Two angles plus a non-included side (AAS) caused an error message instead of a result. The ambiguous SSA case reported only one of its two triangles; both are now shown. The description of the SSA method in the FAQ was reworded.
  • Special Right Triangles: The 30° and 60° labels on the 30-60-90 diagram were swapped. In 30-60-90 mode the only leg option was treated as the hypotenuse; you can now choose short leg, long leg or hypotenuse.
  • Unit Circle: The plotted point and angle arc were mirrored top to bottom, so 90° appeared at the bottom of the circle. tan, sec, csc and cot showed a very large number instead of "undefined" at the angles where they are undefined.
  • Right Triangle Calculator: Feet-and-inches results were truncated instead of rounded near a whole inch (5.99 in showed as 5 in). Pressing Calculate repeatedly drifted the results by re-solving from rounded values. The 3-4-5 reference diagram labelled the sides and angles differently from the calculator, and the θ marker on a second diagram sat on the right angle.
  • Stair Stringer: The IRC maximum flight rise of 12 ft 7 in was given as 147 in; it is 151 in. The worked example recommended a 14 ft (168 in) board for a 169 in stringer; it now recommends 16 ft. The 5 in minimum throat is described as common practice rather than an IRC requirement.
  • Law of Sines, Law of Cosines, Isosceles: Static example diagrams were not drawn to scale for the values in their labels. Redrawn to scale.
  • Several calculators: Obtuse triangles could be drawn partly outside the diagram. Division by zero was not guarded in the arc length and roof pitch tools.

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