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Algebra
Balancing EquationsSimultaneous EquationsDistributive PropertyFactoring QuadraticsCommon FactorDifference of SquaresFactor by GroupingCompleting the SquareQuadratic FormulasCubic FormulasPower Formulas
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Geometry
Area of a Triangle
Trigonometry
SAS Triangle AreaSin, Cos, TanHow Sine Is Derived
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How Pi Is DerivedArea of a CircleArea of a SectorPerimeter of a SectorRadians
Arc Length
Angle from Arc Length

Right triangle ratios

Name the sides from one angle

opposite, adjacent, hypotenuse
thetaadjacentoppositehypotenuseSOH CAH TOAsin = opposite / hypotenusecos = adjacent / hypotenusetan = opposite / adjacentchoose theta, then name the sides

Pick an angle first. The hypotenuse is across from the right angle, the opposite side is across from your chosen angle, and the adjacent side touches it.