MHB What is the formula for finding the area of a circle?

  • Thread starter Thread starter mathland
  • Start date Start date
  • Tags Tags
    Area Circle
AI Thread Summary
The discussion centers on finding the area of a circle using the formula A = πr². The user initially miscalculates the radius by incorrectly relating the diameter to the circumference. They clarify that the diameter is 10, not 10π, leading to the correct calculation of the radius as 5. The error in cubing π in the area calculation is acknowledged, emphasizing that the area should not involve volume. The thread concludes with the user recognizing their mistake and expressing gratitude for the correction.
mathland
Messages
33
Reaction score
0
FB_IMG_1611801510361.jpg


My Effort:

Circumference = pi•d

10 •pi = pi•d

10•pi/pi = d

10 = d, where d is the diameter of the circle.

Area = pi•r^2, where r is the radius of the circle.

Diameter = 2 times the radius.

10pi = 2r

10pi/2 = r

5pi = r

A = pi•r^2

A = pi(5pi)^2

A = 25•pi^3, which makes no sense.

Only the volume is cubed. This is not a volume question.
 
Mathematics news on Phys.org
mathland said:
Circumference = pi•d
10 •pi = pi•d
10•pi/pi = d
10 = d[/color], where d is the diameter of the circle. Correct![/color]
Area = pi•r^2, where r is the radius of the circle.
Diameter = 2 times the radius.
10pi[/color] = 2r Wrong![/color]
The diameter is 10, not 10pi.
 
Opalg said:
The diameter is 10, not 10pi.

I see my error. Thanks.
 
Suppose ,instead of the usual x,y coordinate system with an I basis vector along the x -axis and a corresponding j basis vector along the y-axis we instead have a different pair of basis vectors ,call them e and f along their respective axes. I have seen that this is an important subject in maths My question is what physical applications does such a model apply to? I am asking here because I have devoted quite a lot of time in the past to understanding convectors and the dual...
Fermat's Last Theorem has long been one of the most famous mathematical problems, and is now one of the most famous theorems. It simply states that the equation $$ a^n+b^n=c^n $$ has no solutions with positive integers if ##n>2.## It was named after Pierre de Fermat (1607-1665). The problem itself stems from the book Arithmetica by Diophantus of Alexandria. It gained popularity because Fermat noted in his copy "Cubum autem in duos cubos, aut quadratoquadratum in duos quadratoquadratos, et...
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. In Dirac’s Principles of Quantum Mechanics published in 1930 he introduced a “convenient notation” he referred to as a “delta function” which he treated as a continuum analog to the discrete Kronecker delta. The Kronecker delta is simply the indexed components of the identity operator in matrix algebra Source: https://www.physicsforums.com/insights/what-exactly-is-diracs-delta-function/ by...
Back
Top