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Math

Math Snap

PROBLEM

11. Given the functions f(x)=cosxf(x)=\cos x and g(x)=10+xg(x)=\sqrt{10+x}, determine the value of g(f(π))g(f(\pi)).
(a.) 3
b. 9
c. 11\sqrt{11}
d. π\sqrt{\pi}
12. If f(x)f(x) and g(x)g(x) are even functions, then what type of function is y=f(x)g(x)y=f(x)-g(x) ?
a. odd
b. even
c. neither
d. cannot be determined for sure
13. To solve the inequality f(x)>g(x)f(x)>g(x), a student could graph the combined function y=f(x)g(x)y=f(x)-g(x) and identify the portions of the graph that are below the xx-axis.
a) True
b) false
14. If f(x)f(x) and g(x)g(x) are both functions that are defined for all xRx \in \mathbb{R}, then f(g(x))=g(f(x))f(g(x))=g(f(x)).
a) True
b) false
15. If f(x)f(x) is a function that is defined for all xRx \in \mathbb{R}, then ff1(x))=x\left.f f^{-1}(x)\right)=x.
a) True
b) false

STEP 1

What is this asking?
We're plugging π\pi into cos(x)\cos(x), and then plugging that result into g(x)=10+xg(x) = \sqrt{10 + x}.
Watch out!
Make sure to evaluate the functions from the inside out!
Also, remember what cos(π)\cos(\pi) equals.

STEP 2

1. Evaluate f(π)f(\pi)
2. Evaluate g(f(π))g(f(\pi))

STEP 3

Alright, so we start with our function f(x)=cos(x)f(x) = \cos(x).
We want to find f(π)f(\pi), which just means plugging in π\pi for xx.
So, we get f(π)=cos(π)f(\pi) = \cos(\pi).

STEP 4

Now, remember the unit circle!
At π\pi radians, the x-coordinate is -1, which is precisely the value of cos(π)\cos(\pi).
So, f(π)=cos(π)=1f(\pi) = \cos(\pi) = \mathbf{-1}.
Awesome!

STEP 5

We know that g(x)=10+xg(x) = \sqrt{10 + x} and we just found that f(π)=1f(\pi) = \mathbf{-1}.
This means g(f(π))g(f(\pi)) is the same as g(1)g(\mathbf{-1}).

STEP 6

Let's plug in 1\mathbf{-1} for xx in g(x)g(x).
We get g(1)=10+(1)g(\mathbf{-1}) = \sqrt{10 + (\mathbf{-1})}.

STEP 7

Inside the square root, we have 10+(1)=101=910 + (\mathbf{-1}) = 10 - 1 = \mathbf{9}.
So, our expression becomes 9\sqrt{\mathbf{9}}.

STEP 8

Finally, the square root of 9\mathbf{9} is 3\mathbf{3}!
So, g(f(π))=g(1)=10+(1)=9=3g(f(\pi)) = g(\mathbf{-1}) = \sqrt{10 + (\mathbf{-1})} = \sqrt{\mathbf{9}} = \mathbf{3}.
We did it!

SOLUTION

The value of g(f(π))g(f(\pi)) is 3\mathbf{3}.

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