 I am Professor S.P. Mankhani, Assistant Professor, Department of Mechanical Engineering, Valchain Institute of Technology, Solapur. Today, we are going to study projection of perpendicular lines. So, at the end of this session, student will be able to understand how to draw projection of perpendicular lines. So, now the question is given in this particular problem as line AB in front view as well as in top view, they are given the diagram. So, as far as in the front view is concerned, we are going to be writing it as AFBF and in the top view, AHBH. In addition to that one, one more point is given as CH. Here, the given condition are line AB that is AHBH and AFBF. Means AHBH and AFBF is already printed on the question paper. It is a printed, this is a given condition. Top view of the other line that is BHCH. So, this is BHCH. This is a given condition. Now, they are expected as you have to draw the, this C point, locate the C point in the front view as well as to draw the perpendicular line. Sometimes that perpendicular line, they are going to be given as a dimension of the line is also concerned. So, now we are going with this particular problem. So, here this is a given condition. So, here the XY line and this is a front view and this one is a top view. So, in these two figures, the additional is C point is given in the top view. Here, we have to identify the position of the C point is concerned in the front view. So, now here you have to draw the projection lines from A as well as B. So, this projector line coming and it is going to touch the AHBH in the top view and it is BF is going to touch the BH. This is the projector line you have drawn it. So, now then we have to make it here as this is a new X1, Y1 line. Here it is a X1, Y1 line which is parallel to this AFBF line. We have to set the drafter to this line then bring the drafter at a certain position here. Then you draw the X1, Y1 new reference line. The meaning is that this XY line is a reference line previously. The same line you have brought it here and made it to the parallel to this one. So, when it becomes parallel to this one whatever the view we are going to be getting here that is a true length. In this problem to draw a perpendicular line to the given line the one line must be a true length. One line must be a true length. This line we are going to make it as a true length. So, that is the reason we have brought it this line. We have made it this line as a parallel to the X1, Y1 line. Means we have drawn this as X1, Y1 as a new reference line parallel to this. So, this gap you does not have any distinction you can take anywhere as per your convenient. But only consideration as you should have such a distance that you should not overlap unnecessary on the existing line work. So, that is the reason I have taken in this position. If you take a bit away you are going to be crossing the diagram this particular drawing sheet is concerned. To avoid that one you take in such a position that it should be feasible to get the figure here. So, now we have to draw it the projector line. So, from AF, BF you have drawn the projector line on new X1, Y1 line. So, now we are going to be identifying the position of this A point as well as B point in this particular position. So, here for completing this figure you have to refer previous to previous diagram. For completing this figure refer previous to previous. So, for this diagram this is previous and previous to previous is this diagram. By referring this diagram you are going to be transferring the position of AH as well as BH on this particular projectors. So, now we are going for the measurement of keeping the compass here at this particularly intersection point of X1, XY and AH projector line. So, it will intersect here take it this dimension. So, then this dimension is now we are going to be representing this dimension as a notation given as N. So, this N notation point you are going to be taken here this length and transfer the same by keeping the compass at this particular point. Means the projector line and new X1, Y1 line it is going to intersect at this particular point. Keep the compass here on this particular point and take it this dimension transfer here. So, this is the length of same as that of this length you have transfer this. So, that you are going to be getting this particularly position as this A point here. So, that you are going to be locating as a A1 point here. Similarly, we are going for the B point also to get a B point you have to refer previous to previous this one. Means for completing this figure you are referring previous as this one previous to previous this. So, B point is here keeping the compass at this particularly where the projector line intersect the XY line. Keep the compass here and take it this dimension by taking this particular dimension transfer the same dimension here. Now, just you can observe it this dimension is we are given as a P point this point is given as a P the length you are given notation as a P. So, bring it this dimension and keep the compass here on this particular intersecting point then transfer to on this line. That is a length is given as approximately as a P dimension you have to transfer on this one. So, that you are going to be getting this point as a B point locate that B1 point. So, now A1 B1 line if you are going to join this A1 B1 line it is nothing but a true length. Because the previous view the front view line is parallel to the reference line. So, that here you are going to be getting as a true length. This is the major requirement to draw a perpendicular line to draw a perpendicular line one line must be a true length. Now, we have got this as a true length now for this one setting the drafter bring the drafter on this particularly A1 and B1. Set the drafter on this particularly A1 and B1 then another edge of the drafter is going to be given a 19 degree angle. So, this is a line as a 90 degree line, but the distinction is there as this length is not defined now. This is just you have drawn the line as 90 degree line, but the length of this line is not mentioned at this stage. So, now we are going for the length of this one as for completing this figure refer previous to previous diagram. So, here the point CH is given here. So, now you take it this dimension as CH. So, this is given the notation as a M keeping the compass at the point as on the projector line. If you drawn the projector line from here wherever it will intersect the XY line. So, there from there you have to take it this distance as if you are taken the same distance as by keeping the compass here and making this point as horizontally line this is a M dimension. Now, we have to transfer this M dimension the length of this line is M we have to transfer on this particularly. Just parallel to this one just you draw the horizontal line which is having a dimension as M distance from this X1 Y1 line. So, now you have drawn this as a M distance and this is a parallel line which is parallel to the new X1 Y1 line. So, when you draw this is a M distance line a new this is a M distance line to the X1 Y1 the reference line and which is parallel to this XY line. So, that it is going to intersect the perpendicular line which you have drawn previously. So, it is going to cut at this particular point this is the point of C1 which is expected in this particular problem is concerned. So, now this point you are going to be locating as a C1 point. So, now you got it as A1 B1 C1 is a perpendicular lines A1 for A1 B1 B1 C1 is perpendicular line which is a 90 degree line this is expected in the problem. So, what you are done in this up to now is for completing this figure you are referred previous to previous diagram. If you refer this diagram you are going to be transferring to this particularly point. So, now A1 B1 C1 is a perpendicular lines A1 B1 is a given line. Now, it is a true length this line is a true length for this one you have set the drafter and then you have drawn this as the B1 C1 as a perpendicular line. And this dimension you have taken from the previous to previous as this dimensions. So, now in this problem they are expected as you have to transfer this C1 back on this particular figure in the front view. So, that you are going to be getting a position of C1 here also because the position of C1 is not given in the front view only given in the top view. So, that because of that one to project this line in the backward direction. So, this is a projection of C1 point means anywhere on this line C1 you are going to get it anywhere on this line this Cf you are going to be getting it. You have drawn the projection from the C1 then you are going to be getting Cf point on this particular projector. So, now you draw the projector from this particular point in the upward direction it is going to cut this line it is going to cut at here. So, that you are going to get it this point as Cf this point as a Cf point you are going to get it. So, join this point with the Bf point Cf Bf is the position of the line in the front view is the position of the line in the front view. But it is not 90 degree it is not 90 degree because this A of Bf is not a true length because this A h B h is not a parallel to the x y line. The condition is one of the line must be true length that is what we have made the construction work as here then you have taken this as a line as a true length then you have drawn this as a perpendicular line. So, coming back to this one join this line as Cf Bf Cf Bf is indicating it as a I given as a black color here just for indication as you have drawn the new lines. Initially red color line you are given as the lines as given conditions. So, that now you have got the position of Cf C h and Cf is a projector line. So, now based on this one the additional point is given here that is the reason you are forwarded in this direction. If supposed to be instead of this point if they are given in the point is Cf and they are not given the point of this one how you are going to get the solution of this particular problem. The question is instead of giving the C h here if they are given Cf and they are not given C h how you are going to complete the diagram. So, that now if they are given as this point they are not given this point. So, when they are given this condition that time you have proceeded the problem in this direction figure number one figure number two figure number three. So, instead of that one this is that time it becomes as a figure number one this is a figure number two. Then you are going a parallel line with this one x y the new x 1 y 1 line this side and the figure is going to be developing this side. Instead of following this side your figure is going to develop this side that time. So, that you are in a position to now understand this particularly how to draw the perpendicular lines. So, this is just a explanation I given it about this particularly how you have constructed this line in the wording. You can refer this for the detail the construction work. Thank you.