Ключевые слова: algebra, background, blackboard, board, calculation, chalk, classroom, complex, division, drawing, education, equal, equation, formula, function, geometry, graph, handwriting, handwritten, ink, knowledge, laboratory, manuscript, math, mathematics, natural, number, pen, physics, plot, plus, problem, proof, pyramid, school, science, sign, solution, spiral, student, study, technical, texture, theorem, trigonometry, white, writing,