The figure above shows two lines intersecting at the point O. If the lines are rotated about O at the same rate and in the directions shown until AB is perpendicular to CD , through how many degrees must each line move ? A) 90 -Î˜ b) 90 -Î˜/2 C) 90 +Î˜/2 d) (90+Î˜)/2 e) (90+2Î˜)/2 Explanations are welcomed.Thank you Answer : D

Let theta be @ here. First think how much angle will it be required for each line to be coincident. it will be @/2. After both lines become coincident if you rotate each in the mentioned direction by 90/2 = 45 to get AB perpendicular to CD. Thus the answer will be 45+@/2 or (90+@)/2. IMOD

suppose angle b/w the lines is 0. i.e. both lines lie on one another. now wee need to move both lines in opposite direction, so that they are perpendicular. a careful observation will tell that both line sud move 45 degree. so, in the given options, put theta = 0 and see which option gives you 45. it is D.

naveendevaraj wrote: The figure above shows two lines intersecting at the point O. If the lines are rotated about O at the same rate and in the directions shown until AB is perpendicular to CD , through how many degrees must each line move ? A) 90 -Î˜ b) 90 -Î˜/2 C) 90 +Î˜/2 d) (90+Î˜)/2 e) (90+2Î˜)/2 Explanations are welcomed.Thank you Answer : D Plug in Î˜ = 10. Since the lines are rotating toward each other, in order to become perpendicular, they must cover the 10 degrees between them and then rotate 90 degrees more: 10+90 = 100 degrees. So each line must rotate 100/2 = 50 degrees. This is our target answer. Now we plug Î˜=10 into all the answers to see which gives us our target of 50. Only answer choice D works: (90+Î˜)/2 = (90+10)/2 = 50. The correct answer is D.