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Learn to graph and analyze trigonometric functions sin(x), cos(x), tan(x) based on unit circle values. Understand key properties like periods, amplitudes, and phase shifts.
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Similar to other functions, we can graph the trig functions based on values that occur on the unit circle • For this section, we will the notation: • sin(x) • cos(x) • tan(x) • Etc…
Basic Properties • For the input variable x, we will use values of 0 ≤ x ≤ 2π • We will evaluate each function, just like a standard function from before • Form an ordered pair, (x, f(x)) OR (x, y)
Graphing sin(x) • Before we can graph sin(x), lets actually fill in the different values that occur on the unit circle
Graphing cos(x) • Before we can graph cos(x), lets actually fill in the different values that occur on the unit circle • Look at any similarities
Graphing tan(x) • To graph tan(x), we have to consider the equation tan(x) = sin(x)/cos(x) • Using our two tables, let’s compile a table for tan(x)
Why are there “gaps” in the tangent function? • Where else/what ever trig functions may the “gap” reappear
Combine • Let’s combine the graphs for sin(x) and cos(x)
Terminology • Periodic = a function f is said to be periodic if there is a positive number p such that f(x +p) = f(x) • When values repeat • Different x values for the same y-value
Periods • For sin(x), cos(x), the period is 2π • For the function f(x) = sin(bx – c) or g(x) = cos(bx – c) • Period = 2π/|b|
Example. Determine the period for the function f(x) = 3sin(3x – 2) • Example. Determine the period for the function g(x) = 10cos(8x + 1)
Terminology Continued • Amplitude = distance between the x-axis and the maximum value of the function • For the function f(x) = asin(x) or g(x) = acos(x), the value |a| is the amplitude
Example. Determine the amplitude for the function f(x) = 10sin(2x) • Example. Determine the amplitude for the function g(x) = -14.2cos(9x)
Terminology, 3 • Phase Shift = a change in the starting and stopping points for the period of a function • For the function f(x) = asin(bx – c) and g(x) = acos(bx – c); • Phase Shift = c/b
Example. Find the phase shift for the function f(x) = -2cos(πx + 3π) • Example. Find the phase shift for the function f(x) = 9sin(5πx - 9π)