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Antiderivative & Indefinite Integrals. Chapter 3.9 pgs. 119 – 122 Brandon Kyle. You can actually use this stuff.
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Antiderivative & Indefinite Integrals Chapter 3.9 pgs. 119 – 122 Brandon Kyle
You can actually use this stuff • Antiderivatives can be used in the real world when given the acceleration of an object (such as an object in freefall will have the acceleration of gravity, -9.81 m/s2) you can find the velocity, or if given the velocity, you can find the distance traveled.
You will learn how to find the original function, when given the derivative of a function. If f’(x) or f-prime is given, you can find f(x).
The past • Earlier in chapter 3, you learned how to find the derivative of a function when given a function. Now you will learn how to find a function when given the derivative of the function. This is called the antiderivative. • Some tricky parts in this section will be the antiderivatives of trig. functions. Keep in mind the properties of section 3.6 which says that deriv of sine = cosine, however the deriv of cosine = -sine, and also that you are working backwards
Typical Problem • Given: f’(x) = x4 find f(x) = ? • In general, do the opposite of taking the derivative • Derivative: nxn-1 Antiderivative: (xn+1)/n +1 • Therefore f(x) = (1/5)x5 + C • Always add C because deriv of C = 0
Trig. problem • Given: f’(x) = sin(x), find f(x) = ? • If cos(x) d/dx = -sin(x), then • –cos(x) d/dx = sin(x) • So f(x) = -cos(x)
Trig. Problem cont. • Given: f’(x) = sin(5x), find f(x) = ? • d/dx(5x) * ? = 1 • ? = 1/5 • d/dx ? = sin, ? = -cos • Keep inside function(5x) • so: f(x) = -1/5cos5x
Step by step, day by day • Add 1 to exponent (f’(x) = x4, so 4 + 1 = 5) • Divide problem by n + 1(x5 / 5 or (1/5)x5) • Write + C to signify that a constant could have been included(f(x) = (1/5)x5 + C)
Sky diving w/o a parachute (oh nooo) Given: v(t) = -9.81t, where v(t) is meters per second, and t is time. • Find distance fallen after 2 sec. • Antiderivative of velocity is position function, v(t) = p’(t) • p(t) = ?
Sky diving cont. • p(t) = -4.9t2 + C • p(2) = -4.9(2)2 + C = -19.6 + C • position at 2 sec = -19.6 m/s
Now you know… • Now you should know how to find a function or antiderivative when given the derivative of the function.