Among the problems addressed by Vieta with this method is the complete resolution of the quadratic equations of the form X^2 + X b = c and third-degree equations of the form X^3 + aX = b (Vieta reduced it to quadratic equations). He knew the connection between the positive roots of an equation (which, in his day, were alone thought of as roots) and the coefficients of the different powers of the unknown quantity (see Vieta's formulas and their application on quadratic equations). He discovered the formula for deriving the sine of a multiple angle, knowing that of the simple angle with due regard to the periodicity of sines. This formula must have been known to Vieta in 1593.