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I have 1 and 2 graphs up there just to show how they are graphing it
1. y = 3sin [ (1/2) x ] - 5
This is the normal sine function with an amplitude of 3.....shifted down 5 units ....and with a period twice as long as the normal function
A max y value will be when x = pi = 3.14 ....so y = -2
And a min y value occurs at x = 3 pi = 9.42.....so y will be = - 8
So the midline will be at y = [ -2 - 8 ] / 2 = -10/2 = -5
The first point will be at ( 0, - 5)
The second point [going from left to right ] will be a max and will occur at (pi, -2) = (3.14, -2)
Here's the graph : https://www.desmos.com/calculator/jeq6vpldcz
2. y = 3cos(2x) - 1
This is the normal cosine graph with a period of pi (3.14)....an amplitude of 3...and shifted down 1 unit
A max occurs at (0, 2)
A min occurs at ( pi/2, - 4) = (1.57, -4)
So.....the midline is (2 - 4) / 2 = -2/ 1 = -1
So...the first point will occur at (pi/4, -1) = (.785, -1)
And the next point [ going from left to right ] is a min and will occur at ( pi/2, -4) = (1.57, -4)
Here's a graph : https://www.desmos.com/calculator/o492neu3zh