[tex]The\ perimeter\ of\ any\ polygon\ is\ the\ sum\ of\ the\ lengths \\of\ all\ its\ sides\ (a,\ b,\ c,\ d,\ ...)\\\\triangle:\ \ \ P=a+b+c\\\\equilateral\ triangle:\ \ \ P=3a \\\\rectangle:\ \ \ P=2a+2b \\\\square:\ \ \ P=4 a\\\\diamond :\ \ \ P=4a\\\\trapez:\ \ \ P=a+b+c+d\\\\isosceles trapezoid:\ \ \ P=a+b+2c\ \ \ \ \ (c-arm length)\\\\any\ polygon:\ \ \ P=a+b+c+d+...\\----------------\\The\ perimeter\ of\ a\ circle:\ \ \ P=2 \pi r\ \ \ \ \ (r-radius\ or\ a\ circle)[/tex]
