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VL_91125951-Visitor
1-Visitor
May 11, 2021
Solved

Help regarding root function or find function

  • May 11, 2021
  • 1 reply
  • 2581 views

I have the following equations and i am trying to ge the values for b2 and D2.

I have all the other necessary values but i cannot get to solve this.

Have i mistyped the root equation?
I tried with the find function too.

 

Best answer by LucMeekes

Some errors:

1. You've type rectangular brackets here:

LucMeekes_1-1620754934549.png

(around the theta function). Don't ever do that unless you want to create a matrix.

2. Your equations are NOT unit balanced with the given guess values for b2 and D2, set them to be 1 m each to correct that.

3. The root function can solve only ONE variable, not two, and not an expression (like b2/D2)...

In this case you can pull a trick to solve it with root anyway: Multiply the first equation on both sides with D2^2, then the left hand segment becomes equal to the right-hand segment of the second, and we can solve for D2:

LucMeekes_2-1620755412773.png

Now we know D2, we can solve b2 with:

LucMeekes_3-1620755445685.png

 

Or you can look up how to use a solve block in Prime poperly, and use that.

Or you can solve the set symbolically, like I showed in my first reply.

 

Success!
Luc

 

 

 

1 reply

L
LucMeekes23-Emerald IV
23-Emerald IV
May 11, 2021

Please attach the Prime worksheet, not just a picture.

 

Success!
Luc

 

Apart from that, there appear to be two possible solutions:

LucMeekes_0-1620754355980.png

 

V
VL_91125951-VisitorAuthor
1-Visitor
May 11, 2021

Hello,

 

Here is the requested file.

 

L
LucMeekes23-Emerald IVAnswer
23-Emerald IV
May 11, 2021

Some errors:

1. You've type rectangular brackets here:

LucMeekes_1-1620754934549.png

(around the theta function). Don't ever do that unless you want to create a matrix.

2. Your equations are NOT unit balanced with the given guess values for b2 and D2, set them to be 1 m each to correct that.

3. The root function can solve only ONE variable, not two, and not an expression (like b2/D2)...

In this case you can pull a trick to solve it with root anyway: Multiply the first equation on both sides with D2^2, then the left hand segment becomes equal to the right-hand segment of the second, and we can solve for D2:

LucMeekes_2-1620755412773.png

Now we know D2, we can solve b2 with:

LucMeekes_3-1620755445685.png

 

Or you can look up how to use a solve block in Prime poperly, and use that.

Or you can solve the set symbolically, like I showed in my first reply.

 

Success!
Luc

 

 

 

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