Chapter 6: Problem 65
What is meant by the order of a matrix? Give an example with your explanation.
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Chapter 6: Problem 65
What is meant by the order of a matrix? Give an example with your explanation.
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Explain how to find the multiplicative inverse for a \(3 \times 3\) invertible matrix.
Determinants are used to find the area of a triangle whose vertices are given by three points in a rectangular coordinate system. The area of a triangle with vertices \(\left(x_{1}, y_{1}\right),\left(x_{2}, y_{2}\right),\) and \(\left(x_{3}, y_{3}\right)\) is $$\text { Area }-\pm \frac{1}{2}\left|\begin{array}{lll}x_{1} & y_{1} & 1 \\\x_{2} & y_{2} & 1 \\\x_{3} & y_{3} & 1\end{array}\right|$$ where the \(\pm\) symbol indicates that the appropriate sign should be chosen to yield a positive area. Use determinants to find the area of the triangle whose vertices are \((1,1),(-2,-3),\) and \((11,-3)\)
Use a graphing utility to find the multiplicative inverse of each matrix. Check that the displayed inverse is correct. $$\left[\begin{array}{rr}-4 & 1 \\\6 & -2\end{array}\right]$$
Exercises \(77-79\) will help you prepare for the material covered in the first section of the next chapter. Complete the square and write the circle's equation in standard form: $$x^{2}+y^{2}-2 x+4 y-4$$ Then give the center and radius of the circle and graph the equation.
Determinants are used to show that three points lie on the same line (are collinear). If $$\left|\begin{array}{lll}x_{1} & y_{1} & 1 \\\x_{2} & y_{2} & 1 \\\x_{3} & y_{3} & 1\end{array}\right|=0$$ then the points \(\left(x_{1}, y_{1}\right),\left(x_{2}, y_{2}\right),\) and \(\left(x_{3}, y_{3}\right)\) are collinear. If the determinant does not equal 0 , then the points are not collinear. Are the points \((-4,-6),(1,0),\) and \((11,12)\) collinear?
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