numbers and algebraic expressions
logic, sets, intervals
function and its properties
limits of sequences and functions
derivative and integral of functions
elements of statistics
In regular pentagon all sides and angles are the same. The area A = 5/4 * a^2 * ctg 36°. Regular pentagon inscribed in a circle. Constructing. The angles in regular pentagon: 360° : 5 = 72°; 54° + 54° + 72° = 180°.