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In the diagram, f(x) = 2 (x-45^) is drawn for the interval x [-180^ ; 180^]. Write down the amplitude of f.

Mathematics

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5 parts
7.2

−45∘≤x≤135∘-45^\circ \le x \le 135^\circ

7.5

2 solutions2 \text{ solutions}

7.6

x=−45∘ and x=135∘x = -45^\circ \text{ and } x = 135^\circ

Step-by-step solution

14 steps

Part 7

Part 7.12

Write down the amplitude of ff.

The function is given by f(x)=2sin⁡(x−45∘)f(x) = 2 \sin(x - 45^\circ).
For a sine function of the form y=Asin⁡(Bx+C)+Dy = A \sin(Bx + C) + D, the amplitude is ∣A∣|A|.
In this case, A=2A = 2.
The amplitude of ff is 2.

2\boxed{2}

Part 7.2

−45∘≤x≤135∘-45^\circ \le x \le 135^\circ

Determine the values of xx, in the interval x∈[−180∘;180∘]x \in [-180^\circ; 180^\circ], for which f′(x)≥0f'(x) \ge 0.

  1. Find the derivative f′(x)f'(x).

    Given f(x)=2sin⁡(x−45∘)f(x) = 2 \sin(x - 45^\circ).
    The derivative is f′(x)=ddx[2sin⁡(x−45∘)]=2cos⁡(x−45∘)f'(x) = \frac{d}{dx} [2 \sin(x - 45^\circ)] = 2 \cos(x - 45^\circ).

  2. Set f′(x)≥0f'(x) \ge 0.

    We need to solve 2cos⁡(x−45∘)≥02 \cos(x - 45^\circ) \ge 0, which simplifies to cos⁡(x−45∘)≥0\cos(x - 45^\circ) \ge 0.

  3. Find the general solution for cos⁡θ≥0\cos \theta \ge 0.

    Let θ=x−45∘\theta = x - 45^\circ. The cosine function is non-negative in the first and fourth quadrants.
    So, −90∘+360∘n≤θ≤90∘+360∘n-90^\circ + 360^\circ n \le \theta \le 90^\circ + 360^\circ n, where nn is an integer.

  4. Substitute back θ=x−45∘\theta = x - 45^\circ and solve for xx.

    −90∘+360∘n≤x−45∘≤90∘+360∘n-90^\circ + 360^\circ n \le x - 45^\circ \le 90^\circ + 360^\circ n

    Add 45∘45^\circ to all parts:

    −90∘+45∘+360∘n≤x≤90∘+45∘+360∘n-90^\circ + 45^\circ + 360^\circ n \le x \le 90^\circ + 45^\circ + 360^\circ n −45∘+360∘n≤x≤135∘+360∘n-45^\circ + 360^\circ n \le x \le 135^\circ + 360^\circ n
  5. Find the values of xx in the interval x∈[−180∘;180∘]x \in [-180^\circ; 180^\circ].

    For n=0n=0:

    −45∘≤x≤135∘-45^\circ \le x \le 135^\circ

    This interval is within [−180∘;180∘][-180^\circ; 180^\circ].
    For other integer values of nn, the intervals will fall outside [−180∘;180∘][-180^\circ; 180^\circ].

    −45∘≤x≤135∘\boxed{-45^\circ \le x \le 135^\circ}

Part 7.3

On the same set of axes provided in the ANSWER BOOK, draw the graph of g(x)=−tan⁡xg(x) = -\tan x for the interval x∈[−180∘;180∘]x \in [-180^\circ; 180^\circ].

To draw g(x)=−tan⁡xg(x) = -\tan x:

  • Asymptotes: The asymptotes for tan⁡x\tan x are at x=90∘+180∘nx = 90^\circ + 180^\circ n. For g(x)=−tan⁡xg(x) = -\tan x, the asymptotes are the same. In the interval [−180∘;180∘][-180^\circ; 180^\circ], the asymptotes are at x=−90∘x = -90^\circ and x=90∘x = 90^\circ. Draw vertical dashed lines at these x-values.
  • Key points:
    • g(−180∘)=−tan⁡(−180∘)=0g(-180^\circ) = -\tan(-180^\circ) = 0
    • g(−135∘)=−tan⁡(−135∘)=−(−1)=1g(-135^\circ) = -\tan(-135^\circ) = -(-1) = 1
    • g(−45∘)=−tan⁡(−45∘)=−(−1)=1g(-45^\circ) = -\tan(-45^\circ) = -(-1) = 1
    • g(0∘)=−tan⁡(0∘)=0g(0^\circ) = -\tan(0^\circ) = 0
    • g(45∘)=−tan⁡(45∘)=−1g(45^\circ) = -\tan(45^\circ) = -1
    • g(135∘)=−tan⁡(135∘)=−(−1)=1g(135^\circ) = -\tan(135^\circ) = -(-1) = 1
    • g(180∘)=−tan⁡(180∘)=0g(180^\circ) = -\tan(180^\circ) = 0
  • Shape: The graph of g(x)=−tan⁡xg(x) = -\tan x is a reflection of tan⁡x\tan x about the x-axis. It will decrease from positive infinity to negative infinity between asymptotes.
    • From x=−180∘x = -180^\circ to x=−90∘x = -90^\circ: The graph starts at (−180∘,0)( -180^\circ, 0) and decreases towards −∞-\infty as it approaches x=−90∘x = -90^\circ.
    • From x=−90∘x = -90^\circ to x=90∘x = 90^\circ: The graph comes from ∞\infty as it leaves x=−90∘x = -90^\circ, passes through (−45∘,1)(-45^\circ, 1), (0∘,0)(0^\circ, 0), (45∘,−1)(45^\circ, -1), and decreases towards −∞-\infty as it approaches x=90∘x = 90^\circ.
    • From x=90∘x = 90^\circ to x=180∘x = 180^\circ: The graph comes from ∞\infty as it leaves x=90∘x = 90^\circ, passes through (135∘,1)(135^\circ, 1), and decreases to (180∘,0)(180^\circ, 0).

Part 7.43

Write down the value of g(−45∘)−f(−45∘)g(-45^\circ) - f(-45^\circ).

  1. Calculate g(−45∘)g(-45^\circ).

    g(x)=−tan⁡xg(x) = -\tan x g(−45∘)=−tan⁡(−45∘)=−(−1)=1g(-45^\circ) = -\tan(-45^\circ) = -(-1) = 1
  2. Calculate f(−45∘)f(-45^\circ).

    f(x)=2sin⁡(x−45∘)f(x) = 2 \sin(x - 45^\circ) f(−45∘)=2sin⁡(−45∘−45∘)=2sin⁡(−90∘)=2(−1)=−2f(-45^\circ) = 2 \sin(-45^\circ - 45^\circ) = 2 \sin(-90^\circ) = 2(-1) = -2
  3. Calculate the difference.

    g(−45∘)−f(−45∘)=1−(−2)=1+2=3g(-45^\circ) - f(-45^\circ) = 1 - (-2) = 1 + 2 = 3 3\boxed{3}

Part 7.5

2 solutions2 \text{ solutions}

How many solutions does the equation g(x)−f(x)=0g(x) - f(x) = 0 have in the interval x∈[−180∘;180∘]x \in [-180^\circ; 180^\circ]?

The equation g(x)−f(x)=0g(x) - f(x) = 0 is equivalent to g(x)=f(x)g(x) = f(x). We need to find the number of intersection points between the graphs of f(x)f(x) and g(x)g(x) in the given interval.

Let's analyze the graphs:

  • f(x)=2sin⁡(x−45∘)f(x) = 2 \sin(x - 45^\circ):

    • f(−180∘)=2sin⁡(−225∘)=2(22)=2≈1.414f(-180^\circ) = 2 \sin(-225^\circ) = 2(\frac{\sqrt{2}}{2}) = \sqrt{2} \approx 1.414
    • f(−135∘)=2sin⁡(−180∘)=0f(-135^\circ) = 2 \sin(-180^\circ) = 0
    • f(−45∘)=2sin⁡(−90∘)=−2f(-45^\circ) = 2 \sin(-90^\circ) = -2
    • f(0∘)=2sin⁡(−45∘)=−2≈−1.414f(0^\circ) = 2 \sin(-45^\circ) = -\sqrt{2} \approx -1.414
    • f(45∘)=2sin⁡(0∘)=0f(45^\circ) = 2 \sin(0^\circ) = 0
    • f(135∘)=2sin⁡(90∘)=2f(135^\circ) = 2 \sin(90^\circ) = 2
    • f(180∘)=2sin⁡(135∘)=2≈1.414f(180^\circ) = 2 \sin(135^\circ) = \sqrt{2} \approx 1.414
  • g(x)=−tan⁡xg(x) = -\tan x:

    • g(−180∘)=0g(-180^\circ) = 0
    • g(−135∘)=1g(-135^\circ) = 1
    • g(−90∘)g(-90^\circ) is undefined (asymptote)
    • g(−45∘)=1g(-45^\circ) = 1
    • g(0∘)=0g(0^\circ) = 0
    • g(45∘)=−1g(45^\circ) = -1
    • g(90∘)g(90^\circ) is undefined (asymptote)
    • g(135∘)=1g(135^\circ) = 1
    • g(180∘)=0g(180^\circ) = 0

Let's examine the intervals:

  1. x∈[−180∘,−90∘)x \in [-180^\circ, -90^\circ)

    • At x=−180∘x=-180^\circ, f(−180∘)=2f(-180^\circ) = \sqrt{2} and g(−180∘)=0g(-180^\circ) = 0. So f>gf > g.
    • As x→−90∘x \to -90^\circ, f(x)→−2f(x) \to -\sqrt{2} and g(x)→−∞g(x) \to -\infty. So f>gf > g.
    • In this interval, f(x)f(x) decreases from 2\sqrt{2} to −2-\sqrt{2}, while g(x)g(x) decreases from 0 to −∞-\infty. f(x)f(x) remains above g(x)g(x). No intersections.
  2. x∈(−90∘,90∘)x \in (-90^\circ, 90^\circ)

    • As x→−90∘x \to -90^\circ, f(x)→−2f(x) \to -\sqrt{2} and g(x)→∞g(x) \to \infty. So g>fg > f.
    • At x=0∘x=0^\circ, f(0∘)=−2f(0^\circ) = -\sqrt{2} and g(0∘)=0g(0^\circ) = 0. So g>fg > f.
    • At x=45∘x=45^\circ, f(45∘)=0f(45^\circ) = 0 and g(45∘)=−1g(45^\circ) = -1. So f>gf > g.
    • Since g>fg > f at 0∘0^\circ and f>gf > g at 45∘45^\circ, there must be one intersection between 0∘0^\circ and 45∘45^\circ.
    • As x→90∘x \to 90^\circ, f(x)→2f(x) \to \sqrt{2} and g(x)→−∞g(x) \to -\infty. So f>gf > g.
    • In (−90∘,0∘)(-90^\circ, 0^\circ), g(x)g(x) is positive and f(x)f(x) is negative. No intersections.
    • In (45∘,90∘)(45^\circ, 90^\circ), g(x)g(x) is negative and f(x)f(x) is positive. No intersections.
  3. x∈(90∘,180∘]x \in (90^\circ, 180^\circ]

    • As x→90∘x \to 90^\circ, f(x)→2f(x) \to \sqrt{2} and g(x)→∞g(x) \to \infty. So g>fg > f.
    • At x=135∘x=135^\circ, f(135∘)=2f(135^\circ) = 2 and g(135∘)=1g(135^\circ) = 1. So f>gf > g.
    • Since g>fg > f as x→90∘x \to 90^\circ and f>gf > g at 135∘135^\circ, there must be one intersection between 90∘90^\circ and 135∘135^\circ.
    • At x=180∘x=180^\circ, f(180∘)=2f(180^\circ) = \sqrt{2} and g(180∘)=0g(180^\circ) = 0. So f>gf > g.
    • In (135∘,180∘](135^\circ, 180^\circ], f(x)f(x) decreases from 2 to 2\sqrt{2}, while g(x)g(x) decreases from 1 to 0. Since f(x)f(x) is always above g(x)g(x) at 135∘135^\circ and 180∘180^\circ, and both are decreasing, f(x)f(x) remains above g(x)g(x). No intersections.

    Total number of solutions = 0+1+1=20 + 1 + 1 = 2.

    2 solutions\boxed{2 \text{ solutions}}

Part 7.6

x=−45∘ and x=135∘x = -45^\circ \text{ and } x = 135^\circ

Graph hh is obtained when gg is translated 45∘45^\circ to the right. Write down the equations of the asymptotes of hh in the interval x∈[−180∘;180∘]x \in [-180^\circ; 180^\circ].

  1. Determine the equation of h(x)h(x).

    The graph g(x)=−tan⁡xg(x) = -\tan x is translated 45∘45^\circ to the right. This means replacing xx with (x−45∘)(x - 45^\circ).
    So, h(x)=−tan⁡(x−45∘)h(x) = -\tan(x - 45^\circ).

  2. Find the asymptotes of h(x)h(x).

    The asymptotes of tan⁡θ\tan \theta are at θ=90∘+180∘n\theta = 90^\circ + 180^\circ n.
    For h(x)h(x), we set x−45∘=90∘+180∘nx - 45^\circ = 90^\circ + 180^\circ n.

    x=90∘+45∘+180∘nx = 90^\circ + 45^\circ + 180^\circ n x=135∘+180∘nx = 135^\circ + 180^\circ n
  3. Find the asymptotes in the interval x∈[−180∘;180∘]x \in [-180^\circ; 180^\circ].

    • For n=0n=0: x=135∘x = 135^\circ. This is in the interval.
    • For n=−1n=-1: x=135∘−180∘=−45∘x = 135^\circ - 180^\circ = -45^\circ. This is in the interval.
    • For n=1n=1: x=135∘+180∘=315∘x = 135^\circ + 180^\circ = 315^\circ. This is outside the interval.
    • For n=−2n=-2: x=135∘−360∘=−225∘x = 135^\circ - 360^\circ = -225^\circ. This is outside the interval. The equations of the asymptotes of hh in the given interval are x=−45∘x = -45^\circ and x=135∘x = 135^\circ.
    x=−45∘ and x=135∘\boxed{x = -45^\circ \text{ and } x = 135^\circ}
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