Invertiable for all values of theta

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Discussion Overview

The discussion revolves around the invertibility of a specific matrix defined in terms of the angle theta. Participants are exploring the implications of the determinant of the matrix and whether it is non-zero for all values of theta, as suggested by a hint provided in the original post.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • Stephen asks how to show that the matrix B is invertible for all values of theta, referencing a hint about the determinant.
  • One participant claims that the inverse of the matrix is the same as the original but with -θ instead of θ, suggesting that the determinant is always 1.
  • Another participant questions whether the hint about the determinant is being properly considered, prompting a focus on calculating the determinant of the matrix.

Areas of Agreement / Disagreement

There is disagreement regarding the determinant of the matrix B and its implications for invertibility. Some participants assert that the determinant is always 1, while others emphasize the need to calculate it as per the hint provided.

Contextual Notes

Participants have not reached a consensus on the determinant's value or its implications for the matrix's invertibility. The discussion reflects differing interpretations of the hint and the properties of the matrix.

salistoun
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Hi all,

How do you go about solving this question as it says:

Show that the matrix:

| costheta sintheta 0 |
B= | -sintheta costheta 0 |
| 0 0 1 |

is invertible for all values of theta [Hint. Show that det(B) is not equal of all values of theta ]

Thanks

Stephen
 
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Hi Stephen! :smile:
salistoun said:
Show that the matrix:

| costheta sintheta 0 |
B= | -sintheta costheta 0 |
| 0 0 1 |

is invertible for all values of theta [Hint. Show that det(B) is not equal of all values of theta

I don't get it :confused:

everybody knows that the inverse of that is the same but with -θ instead of θ;

and det(B) is always 1.
 
You are given a hint. Did it not occur to you to do what the hint said? What is the determinant of that matrix?
 
salistoun said:
[Hint. Show that det(B) is not equal of all values of theta ]

Is that a typo?
 

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