On solutions of some mathematical problems

Abstract

This article describes the following tasks: some methods for solving equations of the fourth order, the divisibility of the circle 7, the proof of the equation, cos α/2∙cos α/4∙cos α/8∙cos α/16 ∙ ... = 180 cos(90-α)/πα, a Mobius strip, a formula quadrant and triangular number, proof of inequality 2^2a∙a!²/2√a<(2a)!<2^2a∙a!²/√2a, formula amount n-degree integer.