Chapter 11.5, Problem 18HP

To determine

To name a clockwise rotation that is equivalent to a rotation of ${90}^0$ counterclockwise about the origin.

Answer to Problem 18HP

Rotating an equilateral triangle by ${270}^0$ (clockwise)

Explanation of Solution

Given:

A figure

To explain this question, consider an equilateral triangle.

Now, rotating an equilateral triangle by ${270}^0$ (clockwise) about origin:

  

Rotating an equilateral triangle by ${90}^0$ (anticlockwise) about origin:

  

If an equilateral triangle is rotated by ${270}^0$ (clockwise) about origin it will be equivalent to rotating an equilateral triangle by ${90}^0$ (anticlockwise) about origin.

Conclusion:

Hence, rotating a figure by ${270}^{°}$ is equal to rotating the figure by ${90}^{°}.$