Assinale todas as assertivas corretas com relação aos princípios de ensino na Matemática.

kow [346]

There are two acceptable ways of solving this. I'll show both (just in case one of them doesn't align with the information from your textbook).

Option 1 (fast and easy):

The following is the equation for the area of a regular pentagon with side length s.

$A= \dfrac{s^2}{4} \times \sqrt{5(5+2\sqrt{5})}$

Plug s=12 into the equation.

$A= \dfrac{12^2}{4} \times \sqrt{5(5+2\sqrt{5})}$

$\approx 247.7$

The third choice should be your answer.

Option 2 (much more complicated):

The area of a regular polygon can be solved with the following formula.

$A=\dfrac{\text{perimeter} \times \text{apothem}}{2}$

Let's solve for the apothem.

A pentagon can be divided into 5 congruent isosceles triangles. The vertex angle will be 360/5, or 72 degrees.

An isosceles triangle can be divided into two right triangles. One of the angles of the right triangle will be 72/2, or 36 degrees.

The leg opposite of the 36 degree angle will be 12/2, or 6 inches long.

$\text{apothem}=\dfrac{6}{\tan{36}}$

$\approx 8.26$

The apothem is about 8.26 inches.
The perimeter is 12*5, or 60 inches.

$A=\dfrac{\text{perimeter} \times \text{apothem}}{2}$

$=\dfrac{60 \times 8.26}{2}$

$\approx 247.8$

(it seems that we're off by 0.1 due to rounding errors)

The answer is the third choice. Hope this helps! :)

4 0

4 years ago

On February 1, the electricity meter reading for the Smith residence was 19,423 kilowatt hours. On March 1, the meter read 20,28

Karolina [17]

A. How many kilowatt hours of electricity did the Smiths use during February?

Kilowatt hours of electricity the Smiths used during February:
Meter read on March 1 - meter read on February 1 =
20,288 kilowatt hours - 19,423 kilowatt hours =
865 kilowatt hours
Answer: The Smiths used 865 kilowatt hours of electricity during February

b. How many kilowatt hours did they use during March?

Kilowatt hours of electricity the Smiths used during March:
Meter read on April 1 - meter read on March 1 =
21,163 kilowatt hours - 20,288 kilowatt hours =
875 kilowatt hours
Answer: The Smiths used 875 kilowatt hours of electricity during March

8 0

4 years ago

Ava is 23 cm taller than Olivia, and Olivia is half the height of Lucas. If Lucas is 1.78 m tall, how tall are Ava and Olivia? E

Colt1911 [192]

Ava is 1.09 and Olivia is 0.86

3 0

3 years ago

Find x if x-8=2(x+4)

Fofino [41]

Answer:

$x=-16$