Math lesson. Sine and cosine functions. Graphics graphics drawn on the Board

curve, board, line, formula, wave, building, figure, school, exam, test, learning, education, studying, science, learn, points, study, arrows, college, lesson, knowledge, graph, chart, mathematics, class, blackboard, mathematical, algebra, classroom, educate, Sketching, comparison, chalk, calculation, maths, sin, schooling, math, explanation, function, chalkboard, equation, trigonometry, sine, sinus, sinusoid, functions, cos, trigonometric, cosine,