Find Coordinates of Foot of Perpendicular from Point A (-5,5) to Line 10x+2y-3=0

In summary: I apologise in advance for an extremely trivial question, i am returning to brush up on some basic maths and can't seem to arrive at the answerIn summary, the coordinates of the foot of the perpendicular from the point A with coordinates (-5,5) to the line 10x+2y-3= 0 are y=-48, 5y=26.
  • #1
MMCS
151
0
I apologise in advance for an extremely trivial question, i am returning to brush up on some basic maths and can't seem to arrive at the answer

Find the coordinates of the foot of the perpendicular from the point A with coordinates (-5,5) to the line 10x+2y-3= 0

1.) gradient of original line -10/2, gradient of intercepting line 1/5
2.) equation of intercepting line y-5 = 1/5(x+1) *5
3.)5y-25 = x+1 re-arranging gives 5y-x = 26
4.) solve simultaneously -10x-50y=-260 ( *-10 )
10x+2y=3

-48y=-257

y=5.354
Substituting y into either equation
x= -0.7708

From the program i know these answers arnt correct

Any pointers would be appreciated,

Thanks
 
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  • #2
MMCS said:
I apologise in advance for an extremely trivial question, i am returning to brush up on some basic maths and can't seem to arrive at the answer

Find the coordinates of the foot of the perpendicular from the point A with coordinates (-5,5) to the line 10x+2y-3= 0

1.) gradient of original line -10/2, gradient of intercepting line 1/5
2.) equation of intercepting line y-5 = 1/5(x+1) *5
Mistake above. The known point on the intersecting line is (-5, 5), so the equation of this line would be y - 5 = (1/5)(x - (-5))

Why do you have "*5" on the right side of your equation?
MMCS said:
3.)5y-25 = x+1 re-arranging gives 5y-x = 26
4.) solve simultaneously -10x-50y=-260 ( *-10 )
10x+2y=3

-48y=-257

y=5.354
Substituting y into either equation
x= -0.7708

From the program i know these answers arnt correct

Any pointers would be appreciated,

Thanks
 
  • #3
Hi,

I had the *5 to remove the fraction, don't know how i ended up with the 1 on the right hand side. That sorted it. Thanks for spotting that, such a silly mistake. Wouldnt think id been staring at it for half an hour. Probably suggests i need some sleep :bugeye:
 
  • #4
MMCS said:
I apologise in advance for an extremely trivial question, i am returning to brush up on some basic maths and can't seem to arrive at the answer

Find the coordinates of the foot of the perpendicular from the point A with coordinates (-5,5) to the line 10x+2y-3= 0

1.) gradient of original line -10/2, gradient of intercepting line 1/5
2.) equation of intercepting line y-5 = 1/5(x+1) *5

Check the red part.

ehild
 
  • #5
MMCS said:
Hi,

I had the *5 to remove the fraction
If you multiply one side by 5, you need to also multiply the other side by the same number. Maybe you did this, but it doesn't show in your work.

It's best to start a new line when you do this kind of operation.
MMCS said:
, don't know how i ended up with the 1 on the right hand side. That sorted it. Thanks for spotting that, such a silly mistake. Wouldnt think id been staring at it for half an hour. Probably suggests i need some sleep :bugeye:
 

Related to Find Coordinates of Foot of Perpendicular from Point A (-5,5) to Line 10x+2y-3=0

What is the formula for finding the coordinates of the foot of a perpendicular from a point to a line?

The formula for finding the coordinates of the foot of a perpendicular from a point to a line is:
x = (a(1+b^2)-b(c-a))/(1+b^2)
y = (b(a-c)-a(1+b^2))/(1+b^2)
Where a, b, and c are the coefficients of the line equation in the form of ax+by+c=0 and (x,y) are the coordinates of the given point.

How do you determine if the foot of the perpendicular falls within the line segment?

The foot of the perpendicular falls within the line segment if the x-coordinate of the foot is between the x-coordinates of the two points that define the line segment, and the y-coordinate of the foot is between the y-coordinates of the same two points.

What if the line is vertical or horizontal?

If the line is vertical (has an undefined slope), the foot of the perpendicular will have the same x-coordinate as the given point, and the y-coordinate will be the y-intercept of the line.
If the line is horizontal (has a slope of 0), the foot of the perpendicular will have the same y-coordinate as the given point, and the x-coordinate will be the x-intercept of the line.

Can you find the coordinates of the foot of a perpendicular without using the formula?

Yes, you can find the coordinates of the foot of a perpendicular without using the formula by finding the slope of the given line, finding the slope of the perpendicular line (which is the negative reciprocal of the slope of the given line), and then using the point-slope formula to find the equation of the perpendicular line. The coordinates of the foot of the perpendicular will be the point of intersection between the two lines.

Can the foot of the perpendicular be outside of the line segment?

Yes, the foot of the perpendicular can be outside of the line segment. This can happen if the point is located outside of the range of x or y values that define the line segment. In this case, the foot of the perpendicular will be the closest point on the line to the given point.

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