Printable math study guides with every step written out, and free micro-lessons. Written by a teacher of mathematics, typeset like a book.https://acemath.store/en-gbhttps://acemath.store/lessons/the-pythagorean-identity-is-pythagoras/https://acemath.store/lessons/the-pythagorean-identity-is-pythagoras/sin²α + cos²α = 1 is not a new fact to memorise. It is the Pythagorean theorem with both sides divided by c² — and two more useful identities fall straight out of it.Mon, 10 Aug 2026 00:00:00 GMTtrigonometryidentitiespythagorean identitytangenthttps://acemath.store/lessons/the-three-special-angles/https://acemath.store/lessons/the-three-special-angles/Where the exact values of sin, cos and tan at 30°, 45° and 60° come from — derived from half an equilateral triangle and half a square, not memorised.Mon, 10 Aug 2026 00:00:00 GMTtrigonometryspecial anglesexact valuesright trianglehttps://acemath.store/lessons/why-180-degrees-equals-pi/https://acemath.store/lessons/why-180-degrees-equals-pi/A radian is not a conversion factor to memorise — it is the angle standing on an arc as long as the radius. Everything else follows from one line.Mon, 10 Aug 2026 00:00:00 GMTtrigonometryradiansdegreesunit circle