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avatar+204 
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From https://web2.0calc.com/questions/rectangle-abcd-is-the-base-of-pyramid-pabcd-if-ab

 

 

This is a funny lookin pyramid! The formula for the volume of this pyramid is the same as if "P" were above the center of the base:  volume = (1/3)(area of base)(height)

This helped me verify that.

 

Draw AC.

Now look at triangle ABC.  From the Pythagorean theorem....

 

AC2   =   22 + 32   =   4 + 9   =   13

 

AC is in the same plane as AD and AB, so PA is perpendicular to AC.

Look at triangle PAC.  From the Pythagorean theorem again....

 

AC2 + PA2  =  52

13  +  PA2  =  25

PA2  =  12

PA  =  βˆš12

PA  =  2√3

 

And....

volume of pyramid  = (1/3)(area of base)(height)

                               =  (1/3)(  2 * 3  )( PA )

                               =  (1/3)(6)(2√3)

                               =  4√3     cubic units

 

 

I just remembered how my math teacher explained that the volume of an oblique cylinder is the same as the volume of a right cylinder (with the same height and base).

 

Imagine a stack of pennies. If you line the stack straight up, it is a right cylinder. And if you lean the stack over, it is oblique. But the height, area of the base, and the volume stays the same.

 

And in this case, imagine a stack of square pieces of cardboard that get smaller as you go higher. You can stack the squares up to form a right pyramid, or you can slide them to look like the pyramid in this problem. The volume stays the same. 

Dec 10, 2021
 #1
avatar+118654 
+3

At first glance many would say that    p(8)=8/63 which is approx  0.127  but that is not going to be correct.

 

I solved it graphically, though the answer may not be exact.

Here is the link,  It says the polynomial is of degree 4 not 5.  (Even though I specifically asked for degree 5)

I can't check it easily because the coefficients are rounded to 2 decimal places.   indecision

https://www.geogebra.org/classic/fesnhtkm

 

And here is the graph.

 

So this is the approx answer  (or exactly)  f(8)=1/20 = 0.05

 

--------------------------------------

 

 

I also tried to plug the values into a matrix solver calculator but it said matrix A was singular.  To be honest I do't quite know what that means but it didn't give me an answer.  Maybe it did not understand my input.  idk.  

I keep being given a polynomial of degree 4 not 5 maybe this is the problem.

https://www.mathstools.com/section/main/system_equations_solver#.YbKPR71BxnI

 

 

 

Dec 10, 2021

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