FORMULAS FOR SHAPES

Circle

Formulas : 

Area of circle  =  Πr²

Circumference of circle  =  2Πr

Example problems of area of circle

Example problems of circumference of circle

Semicircle

Formulas : 

Area of semicircle  =  Πr² / 2

Circumference of circle  =  Πr

Example problems on semi circle

Quadrant

Formulas : 

Area of quadrant  =  Πr² / 4

Example problems on quadrant

Equilateral Triangle

Formulas : 

Area of equilateral triangle  =  (√3/4)a²

Perimeter of equilateral triangle  =  3a

Example problems on equilateral triangle

Scalene Triangle

Formulas : 

Area of scalene triangle  =  √[s(s-a)(s-b)(s-c)]

Perimeter of scalene triangle  =  a + b +  c

Example problems on scalene triangle

Parallelogram

Formulas : 

Area of parallelogram  =  b x h

Perimeter of parallelogram =  2(a + b)

Example problems of perimeter of parallelogram

Quadrilateral

Formulas : 

Area of quadrilateral  =  (1/2) x d x (h₁ + h₂)

Perimeter of quadrilateral  =  a + b + c + d

Example problems of area of quadrilateral

Rectangle

Formulas : 

Area of rectangle  =  l x w

Perimeter of rectangle  =  2(l + w)

Examples problems on area of rectangle

Examples of perimeter of rectangle

Square

Formulas : 

Area of square  =  a x a

Perimeter of square  =  4a

Examples problems on area of square

Examples problems on perimeter of square

Rhombus

Formulas : 

Area of rhombus  =  (d₁ x d₂) / 2

Perimeter of rhombus  =  4a

Examples problems on area of rhombus

Examples problems on perimeter of rhombus

Trapezoid

Formulas : 

Area of trapezoid  =  h(a + b) / 2

Perimeter of trapezoid  =  a + b + c + d

Examples problems on area of trapezoid

Sector

Formulas : 

Length of arc (l)  = (θ/360) ⋅ 2Πr

When we know the radius "r" of the circle and central angle "θ" of the sector : 

Area of the sector  =  (θ/360°) ⋅ Π r²

When we know the radius "r" of the circle and arc length "l": 

Area of the sector = (l ⋅ r) / 2

Worksheet for length of arc

Area of sector worksheet

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