About SinCosTan

Trigonometry has a reputation for being intimidating, but almost all of it rests on a handful of ideas: a right triangle, a circle of radius one, and the ratios that connect an angle to the sides around it. The trouble is rarely the concept — it’s the arithmetic in the middle, the half-remembered formula, and the “which ratio do I use here?” moment that stalls a homework problem. SinCosTan is built to get you past those moments so the underlying idea can actually land.

Rather than long essays you have to wade through, the site is a set of small, single-purpose calculators, each aimed at one real task. The Right Triangle Calculator solves a triangle from any two values using SOHCAHTOA and the Pythagorean theorem. The Law of Sines & Cosines Calculator handles triangles that aren’t right-angled and flags the ambiguous SSA case. The Degrees to Radians Converter switches units and places the angle on the unit circle. The Sine Wave Calculator breaks a sinusoid into amplitude, period, frequency, phase shift, and midline. The Inverse Trig Calculator turns a ratio back into an angle, and the Trig Function & Identity Calculator evaluates all six functions at once and checks the Pythagorean identity.

Alongside the calculators, the blog and learnsection explain the reasoning the tools rest on — how to read the unit circle, why radians are the natural unit for angles, when to reach for the law of sines versus the law of cosines, and which identities are worth committing to memory. Every explanation is written from scratch and worked through with real numbers.

A few things worth stating plainly. SinCosTan is independent and not affiliated with any school, exam board, or textbook publisher. It is supported by advertising, which is how the tools stay free with no account required. The calculators are learning and checking aids: they show their working and round for readability, but for graded coursework or anything that depends on full precision you should confirm the result by hand or with a full-precision calculator. If a tool looks wrong, or there’s a calculator you wish existed, the contact page is the place to tell us.