numbers and algebraic expressions
logic, sets, intervals
function and its properties
limits of sequences and functions
derivative and integral of functions
elements of statistics
Examples. 80° + 100° = 180°. 70° + 110° = 180°. Derivation. Central angles equal 2γ and 2α based on inscribed angle theorem. Circle circumscribed about a quadrilateral. Quadrilateral inscribed in a circle.