Drawing Lines at the Right Angle

[david18]

For the first two parts of the question I simply used some symmetry to get the lines meeting the mirror at the correct angle. However for part c) whilst I know roughly what it should look like the angles aren't very accurate. Is there any simple method like the use of symmetry to draw lines at the right angle?

 

[Doc Al]

Here's a trick that might help you. A plane mirror produces an image of an object that is directly opposite the object and the same distance inside the mirror. Using that, you can immediately draw the location of the image of P inside mirror Y. Then that image acts as an object as far as mirror X is concerned--draw that second image inside mirror X.

See if that helps.