Find the Equation of a Trigonometric Function Given Its Graph - Grade 12

In this video, it is shown, through an example, how to find the equation of a trigonometric function, given by its graph. The function suggested is of the form: V(t) = A cos (Bt + C) + D where t is the variable. Formulas to find the parameters A (chosen to be positive) and D describing the amplitude and vertical shift of the trigonometric function are deduced: A = (Vmax - Vmin) / 2 , gives A greater than zero. D = A = (Vmax +Vmin) / 2 The period of the function is determined from its graph and the formula: Period = 2 pi / B , B greater than zero. is used to find B. The parameter C is related to the phase shift and is determined by locating a maximum (or a minimum) of the function using the graph. Assume the maximum is at t = T, and write the equation