I understand how to get dimension and frequency, but not sure about phase changes? How does it get π / 4?

Please advise.

Instructions:

As explained on

1.) Horizontal between two wave actions Measure the changes by graphing them. One change on the right is a positive phase shift and one change on the left is a negative step change.

2.) Determine the phase shift between the cosine function and the sign function. To use the trigonometric identification (x) = sin (x + Pi / 2) to show that we can get the cosine function by moving the sine wave PI / 2 to the left. Therefore, the cosine function - sign function with phase shift of PI / 2.

3.) sinusoidal equation y = Asin (B [X - C]) + D. In this equation, the dimension of the wave is A, the factor of the extension is B., phase The change is si and the amplitude shift is d

4. ) Express a wave function in form Y = Asin (B [x-C]) + D, to determine its phase change c. For example, for function cos (x) = sin (x + pi / 2)) = sin (x - [-p / 2]), we have c = -p / 2 therefore, by-pi / 2 Transferring the phase of the sign function will produce the cosine function.

5.) function y = sin (2x - P / 2). This function is equal to y = sin (2 [x - pi / 4]) where A = 1, B = 2, C = Pi / 4 and D = 0 Y = phase shift of phase (2x - Pi / 2) is therefore PI / 4.