What is the image of point (4, 5) after a counterclockwise rotation of 270º about the origin?

1 answer:

3 0

A counterclockwise rotation of 270º about the origin is equivalent to a clockwise rotation of 90º about the origin.

Given a point (4, 5), the x-value, i.e. 4 and the y-value, i.e. 5 are positive, hence the point is in the 1st quadrant of the xy-plane.

A clockwise rotation of 90º about the origin of a point in the first quadrant of the xy-plane will have its image in the fourth quadrant of the xy-plane. Thus the x-value of the image remains positive but the y-value of the image changes to negative.
Also the x-value and the y-value of the original figure is interchanged.
For example, given a point (a, b) in the first quadrant of the xy-plane, a counterclockwise rotation of 270º about the origin which is equivalent to a clockwise rotation of 90º about the origin will result in an image with the coordinate of (b, -a)

Therefore, a counterclockwise rotation of 270º about the origin of the point (4, 5) will result in an image with the coordinate of (5, -4) (option C)

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The temperature fell from 0 Degrees Fahrenheit to 15 and one-half Degrees Fahrenheit below 0 in 5 and three-fourths hours. Wen t

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Answer:

The correct answer will be:

$-\dfrac{62}{23}$

Step-by-step explanation:

It is given that :

Initial temperature, $T_1 = 0^\circ F$

Final temperature,

$T_2 = -15\dfrac{1}{2}^\circ F\\\Rightarrow T_2 = -\dfrac{15\times 2+1}{2} ^\circ F\\\Rightarrow T_2 = -\dfrac{31}{2} ^\circ F$

Time taken :

$5\dfrac{3}{4}\ hrs = \dfrac{5 \times 4+3}{4}\ hrs = \dfrac{23}{4}\ hrs$

Change in temperature per hour:

$\dfrac{\text{Difference of temperature}}{\text{Total Time Taken}}\\\Rightarrow \dfrac{T_2-T_1}{\text{Total Time Taken}}$

Putting the values of temperatures and time:

$\dfrac{\dfrac{-31}{2}-0}{\dfrac{23}{4}}\\\Rightarrow \dfrac{\dfrac{-31}{2}}{\dfrac{23}{4}}\\\Rightarrow \dfrac{-31 \times 4}{2 \times 23}} \text{---- Error done by Wen at this step}\\\Rightarrow \dfrac{-31 \times 2}{23}}\\\Rightarrow \dfrac{-62}{23}}$