-7(k+9)=9(k-5)-14k
-7k-63=(9k-45)-14k
-7k-63=-5k-45
-7k=-5k+18
-2k=18
k=-9
She asked her friends, which does not represent a random sample.
She tried to show cause and effect without doing an experiment (which includes simple random sample, control group, treatment, etc).
So the answer is she did not use a random sample, and tried to show cause and effect with an observational study.
Answer:
A) If the domain of y=cos(x) is restricted to [0, π], y=cos^-1(x) is a function.
Step-by-step explanation:
In order for the inverse function to be a function, the original must pass the horizontal line test: a horizontal line must intersect the function in only one place.
As you can see from the attached graph, restricting the cosine function to the domain [0, π] allows it to pass the horizontal line test, so its inverse will be a function.
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Restricting the domain to [-π/2, π/2] does not limit cos(x) to something that will pass the horizontal line test.
Probably a circle. Its the same thing as cutting a cube and getting a square, and cross sectioning a pentagonal prism and getting a pentagon.