Math Problem Statement

The function g is defined and differentiable on the closed interval [-7, 5] and satisfies g(0) = 5. The graph of y = g'(x), the derivative of g, consists of a semicircle and three line segments. Find g(3) and g(-2).

Solution

We are given a graph of g(x)g'(x), the derivative of g(x)g(x), and we need to find g(3)g(3) and g(2)g(-2). Additionally, we know that g(0)=5g(0) = 5.

To solve this, we will use the Fundamental Theorem of Calculus, which states:

g(x)=g(0)+0xg(t)dtg(x) = g(0) + \int_0^x g'(t) \, dt

Thus, to find g(3)g(3) and g(2)g(-2), we will integrate g(x)g'(x) over the respective intervals. This will require calculating the areas under the curve of g(x)g'(x), with the convention that areas above the xx-axis contribute positively and areas below the xx-axis contribute negatively.

Finding g(3)g(3):

  1. From x=0x = 0 to x=3x = 3, we integrate the graph of g(x)g'(x).
  2. The graph includes a semicircle and a triangle.
    • The semicircle has a radius of 1 and is above the x-axis (centered at x=0x = 0).
    • The triangle between x=1x = 1 and x=3x = 3 is also above the x-axis.

Step-by-step:

  1. Semicircle (from x=0x = 0 to x=1x = 1):

    • Area of a semicircle is 12πr2\frac{1}{2} \pi r^2, where r=1r = 1, so this gives us: Area of semicircle=12π12=π2\text{Area of semicircle} = \frac{1}{2} \pi \cdot 1^2 = \frac{\pi}{2}
  2. Triangle (from x=1x = 1 to x=3x = 3):

    • The triangle has a base of 2 (from x=1x = 1 to x=3x = 3) and a height of 2.
    • Area of the triangle is: Area of triangle=12baseheight=1222=2\text{Area of triangle} = \frac{1}{2} \cdot \text{base} \cdot \text{height} = \frac{1}{2} \cdot 2 \cdot 2 = 2

Thus, the total area from x=0x = 0 to x=3x = 3 is: π2+2\frac{\pi}{2} + 2

Now, using the fundamental theorem, we have: g(3)=g(0)+03g(x)dx=5+(π2+2)g(3) = g(0) + \int_0^3 g'(x) \, dx = 5 + \left( \frac{\pi}{2} + 2 \right) g(3)=5+π2+2=7+π2g(3) = 5 + \frac{\pi}{2} + 2 = 7 + \frac{\pi}{2}

Finding g(2)g(-2):

  1. From x=0x = 0 to x=2x = -2, we again integrate the graph of g(x)g'(x).
  2. This corresponds to two line segments, both below the x-axis.

Step-by-step:

  1. Line segment from x=0x = 0 to x=1x = -1:

    • This is a straight line with a slope of -1, forming a triangle with base 1 and height 1 below the x-axis.
    • The area of the triangle is: Area=1211=12\text{Area} = \frac{1}{2} \cdot 1 \cdot 1 = \frac{1}{2}
    • Since it's below the x-axis, the area is 12-\frac{1}{2}.
  2. Line segment from x=1x = -1 to x=2x = -2:

    • This is a triangle with a base of 1 and height of 1 below the x-axis.
    • The area is again 12\frac{1}{2}, but negative: Area=12\text{Area} = -\frac{1}{2}

Thus, the total area from x=0x = 0 to x=2x = -2 is: 1212=1- \frac{1}{2} - \frac{1}{2} = -1

Now, using the fundamental theorem: g(2)=g(0)+02g(x)dx=5+(1)=4g(-2) = g(0) + \int_0^{-2} g'(x) \, dx = 5 + (-1) = 4

Final answers:

  • g(3)=7+π2g(3) = 7 + \frac{\pi}{2}
  • g(2)=4g(-2) = 4

Would you like further details or have any other questions? Here are some related questions you might explore:

  1. What if the semicircle had a different radius? How would that affect g(3)g(3)?
  2. How do we apply the Fundamental Theorem of Calculus to other types of graphs?
  3. Can we find the maximum or minimum values of g(x)g(x) using this graph?
  4. What happens if we reverse the limits of integration?
  5. How would the calculation change if g(x)g'(x) had discontinuities?

Tip: When integrating graphically, always pay attention to the areas above and below the x-axis to determine the net contribution.

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Math Problem Analysis

Mathematical Concepts

Integral Calculus
Geometric Area Under Curve
Fundamental Theorem of Calculus

Formulas

g(x) = g(0) + \int_0^x g'(t) dt
Area of semicircle = \frac{1}{2} \pi r^2
Area of triangle = \frac{1}{2} \cdot base \cdot height

Theorems

Fundamental Theorem of Calculus

Suitable Grade Level

Undergraduate Calculus