Give Point To Rotate About:
Select the 'Cen' point (P1) and the prompt reads:
Give Reference Point To Rotate To:
Select the 'Cen' point (P2) and the prompt reads:
Give Point To Rotate To:
Now the polar input mode is automatically selected. Hold down the key (this creates a copy) and move the cursor to the LEFT and around until the angle dimension reads '45.0' and click. The new rotated line is now in place. The original line is still selected so right-click to repeat the command. This time select the same points but move the cursor to the RIGHT and around until the angle dimension reads '315.0' and click (remember to hold to copy).