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Area of a Triangle

½(b×h)

Pythagorean Theorem

a²+b²=c²

Sides in a 30°-60°-90° Triangle

1:√3:2

Sides in a 45°-45°-90° Triangle

1:1:√2

Area of a Circle

πr²

Circumference of a Circle

2πr, or πd

Area of a Parallelogram

b×h

Area of a Trapezoid

{½(b₁+b₂)}h

Area of a Kite or a Rhombus

½(d₁+d₂)

Area of a Square

s²

Area of a Regular Polygon

½(p×a)

Sum (in degrees) of the Interiors Angles of a Triangle

180°

Sum (in degrees) of the Interior Angles in an N-Sided Polygon

(n-2)180

Sum (in degrees) of the Exterior Angles in any Polygon

360°

Number of Diagonals that can be drawn in an N-Sided Polygon

½{n(n-3)}

Slope

rise÷run

Midpoint Formula

(xmp, ymp)

Distance Formula

√(x₂-x₁)²+(y₂-y₁)²

Slope-Intercept Form of the Equation of a Line

y=mx+b

Point-Slope Form of the Equation of a Line

y-y₁=m(x-x₁)

Equation of a Circle

(x-h)²+(y-k)²=r²

Hero's Formula

√S(S-a)(S-b)(S-c)