Branch 06 · free, no sign-up
Trigonometry Calculators
Trigonometry connects angles to lengths. Once you accept that sine and cosine are just ratios of sides, the identities stop being things to memorise and start being things you can check.
Every calculator in this branch is checked by a mathematician before it goes live.
- 135° the angle
- 135 · π⁄180 multiply by π/180 — a half turn is π radians
- 3π⁄4 135/180 reduces to 3/4
Calculators
All 10 trigonometry calculators, by topic
measure the angle first, then the ratios that depend on it
Angles & Measurement
Trig Functions
Identities
Triangle Solving
Where this sits
What comes before trigonometry
each topic assumes the one to its left
Stuck part way through? Start at the leftmost topic you are not sure about — everything to the right depends on it.
Knowledge base
Read the reasoning, not just the answer
one article per question a teacher would answer
Questions
Asked often enough to answer here
the ones that change how you work, not trivia
Why do radians exist if degrees already work?
Because radians measure an angle by the arc it cuts, which makes the calculus of sine and cosine come out clean. In degrees the derivative of sin x picks up an awkward constant; in radians it is simply cos x.
How do I know whether to use the law of sines or cosines?
Count what you know. An angle paired with its opposite side points to the law of sines. Two sides with the angle between them, or all three sides, points to cosines.
Is SOH-CAH-TOA enough?
For right triangles, yes. The moment a triangle has no right angle you need the two laws instead, which is usually where students get stuck.
Nearby
Branches that touch this one
linked because the maths overlaps, not because it fills space