Perimeters And Areas Of Plane Figures

Rectangle: Perimeter = 2(l+b); Area = lb

Square: Perimeter = 4a; Area = a^2; Diagonal = a√2

Triangle (base-height): Perimeter = a+b+c; Area = 1/2 × b × h

Heron's Formula: Area = √(s(s-a)(s-b)(s-c)), s = (a+b+c)/2

Parallelogram: Area = b × h

s = (a+b+c)/2

Area = √(s(s-a)(s-b)(s-c))

Area of path around a rectangle of dimensions l×b with width w = (l+2w)(b+2w) − lb

Area of two cross paths through middle of rectangle = w(l+b) − w^2

For two cross paths, simplified form = w(l+b−w)