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Area and perimeter formulas

14 formulas · what each one means · a free lesson for each

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steplyclass.com/formula-sheets/area-and-perimeter/ · free, step-by-step lessons for every formula

Perimeter and area

Rectangle
P = 2l + 2w A = lw
Perimeter = all the way around; area = length × width.Lesson: Perimeter and area →
Square
P = 4s A = s2
Lesson: Perimeter and area →
Triangle
A = 12bh
Half of base × height; the height meets the base at 90°.Lesson: Perimeter and area →
Parallelogram
A = bh
Base × height (the straight-up height, not the slanted side).Lesson: Parallelogram and trapezoid →
Trapezoid
A = 12h(b1 + b2)
The mean of the two parallel sides × the height.Lesson: Parallelogram and trapezoid →
Rhombus and kite
A = 12d1 d2
Half of one diagonal × the other.Lesson: Rhombus and kite →
Circle: circumference
C = 2πr = πd
The distance around a circle.Lesson: Perimeter and area →
Circle: area
A = πr2
Lesson: Perimeter and area →
Arc length
θ360° × 2πr
The arc is a part of the circumference: θ out of 360°.Lesson: Arc length, sector area and perimeter as a part of the circle →
Sector area
θ360° × πr2
The sector is a part of the circle's area.Lesson: Arc length, sector area and perimeter as a part of the circle →
Composite shapes
add the parts, take away the holes
Split the shape into rectangles, triangles and circles.Lesson: Composite shapes →

Any triangle

Law of sines
asin A = bsin B = csin C
Use with a side and the angle across from it.Lesson: The law of sines →
Law of cosines
c2 = a2 + b2 − 2ab cos C
Use with three sides, or two sides and the angle between.Lesson: The law of cosines →
Area with sine
A = 12ab sin C
Two sides and the angle between them.Lesson: Area of a triangle with sine →

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