What is the area of the largest rectangle that can be inscribed in an isosceles triangle with side lengths $8$, $\sqrt{80}$, and
$\sqrt{80}$? Assume that one side of the rectangle lies along the base of the triangle.
1 answer:
First let's solve the general case for an isosceles triangle of base 2 and height k. If the triangle is drawn so the base is on the x-axis and the apex is on the y-axis, the equation for the line containing the right side is
y = -k(x-1)
Then a rectangle with x-dimension w will have an area that is the product of this width and the height y = -k((w/2)-1).
area = w(-k(w/2 -1)) = (-k/2)w² +kw
The derivative of area with respect to w will be zero where the area is a maximum:
d(area)/dw = 0 = -kw +k
w = 1 . . . . . . add kw and divide by k
Using the formula for area, we find
area = 1(-k(1/2-1)) = k/2
This value is 1/2 the total area of the triangle we started with.
If the side lengths of your triangle are 8, √80, and √80, the height will be given by the Pythagorean theorem as
h = √((√80)² - (1/2·8)²) = √(80-16) = 8
Your triangle's area will be
triangle area = (1/2)(8)(8) = 32
The maximum area of the inscribed rectangle will be half this value,
16 square units
y = -k(x-1)
Then a rectangle with x-dimension w will have an area that is the product of this width and the height y = -k((w/2)-1).
area = w(-k(w/2 -1)) = (-k/2)w² +kw
The derivative of area with respect to w will be zero where the area is a maximum:
d(area)/dw = 0 = -kw +k
w = 1 . . . . . . add kw and divide by k
Using the formula for area, we find
area = 1(-k(1/2-1)) = k/2
This value is 1/2 the total area of the triangle we started with.
If the side lengths of your triangle are 8, √80, and √80, the height will be given by the Pythagorean theorem as
h = √((√80)² - (1/2·8)²) = √(80-16) = 8
Your triangle's area will be
triangle area = (1/2)(8)(8) = 32
The maximum area of the inscribed rectangle will be half this value,
16 square units
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Answer: Terry paid $18.36 for the sweater.
Step-by-step explanation:
Given: Sales price of sweater = $24
Coupon states off the sales, i.e. Terry will get
discount.
Also, tax rate = 6%
Tax will be charged = 6% of Sales price of sweater
= 0.06 x 6
= $0.36
Now , Final amount for Terry = Sales price - discount +tax
= $(24-6+0.36)= $18.36
Hence, Terry paid $18.36 for the sweater.
Answer:
(a) Hence, the margin of error reported by The Marist Poll was correct.
(b) Based on a 95% confidence interval the poll does not provide convincing evidence that more than 70% of the population think that licensed drivers should be required to retake their road test once they turn 65.
Step-by-step explanation:
We are given that the Marist Poll published a report stating that 66% of adults nationally think licensed drivers should be required to retake their road test once they reach 65 years of age.
It was also reported that interviews were conducted on 1,018 American adults, and that the margin of error was 3% using a 95% confidence level.
(a) <u>Margin of error formula is given by;</u>
Margin of Error =
where, = level of significance = 1 - 0.95 = 0.05 or 5%
Standard of error =
Also, = sample proportion of adults nationally think licensed drivers should be required to retake their road test once they reach 65 years of age = 66%
n = sample of American adults = 1.018
The critical value of z for level of significance of 2.5% is 1.96.
So, <em>Margin of Error </em>=
= = 0.03 or 3%
Hence, the margin of error reported by The Marist Poll was correct.
(b) Now, the pivotal quantity for 95% confidence interval for the population proportion who think that licensed drivers should be required to retake their road test once they turn 65 is given by;
P.Q. = ~ N(0,1)
So, <u>95% confidence interval for p</u> =
=
= [0.66 - 0.03 , 0.66 + 0.03]
= [0.63 , 0.69]
Hence, based on a 95% confidence interval the poll does not provide convincing evidence that more than 70% of the population think that licensed drivers should be required to retake their road test once they turn 65 because the interval does not include the value of 70% or more.