Ordinates (1 Viewer)

[Constip8edSkunk]

what are they? i thought they are the y co-ordinates of a point but what do they mean when they say the ordinate of P intersect the asymptote at N or something like that. This is from the blue patel 4U text book.

 

[Bannanafish]

the x value is one ordinate
the y value is another ordinate
together they form a co-ordinate

 

[Newbie]

whats an absisscae ?
i dont even know the spelling of it

 

[underthesun]

Abscissae is supposed to be the x-value of a co-ordinate, but for some reasons, some questions from some textbook (terry*cough*lee*cough) refers to abscissae as the y co-ordinate.. it's strange..

BTW the dictionary says "The value of a coordinate on the horizontal axis"

 

[Constip8edSkunk]

Originally posted by Bannanafish
the x value is one ordinate
the y value is another ordinate
together they form a co-ordinate

but what do they mean when they imply the ordinate is a line? eg. "NP is the ordinate of a point P(x₁,y₁) on the ellipse b²x²+a²y²=a²b²"

Originally posted by Newbie
whats an absisscae ?
i dont even know the spelling of it

the abscissa should be the x coordinate

 

[ND]

Originally posted by Constip8edSkunk
what do they mean when they say the ordinate of P intersect the asymptote at N

With P(asec@, btan@) and asymptote y=bx/a, N would have coords (atan@, btan@).

but what do they mean when they imply the ordinate is a line?

Well you can think of it as a line: from the above example, the parametric coords are x=asec@, y=btan@. Here the ordinate is the line y=btan@, so you want to know where y=btan@ intersects y=bx/a.

 

[Constip8edSkunk]

thats what i thought except they dont seem to fit into the questions...

for example

Patel 6E q5
"NP is the ordinate of a point P(x₁,y₁) on the ellipse b²x²+a²y²=a²b². The tangent at P meets the x-axis at A. Prove that ON.OA=a², where O is the origin."

or

6D q32
the ordinate at P(asec@, btan@) meets the asymptote of the hyperbola b²x²-a²y²=a²b² at Q. The normal at P meets the x-axis at G. Prove that GQ is perpendicular to the asymptote.

 

[ND]

Yeh you're right, however they both work if you consider the ordinate to be the vertical lines (i.e. x=acos@ and x=asec@ in q5 and q32 resp.). I guess when they say ordinate they mean the line parallel with the y-axis.

 

[Constip8edSkunk]

ahhh sweet... thx alot mate

 

[Bannanafish]

well they might make you find the equation of the asymptote, and if it's a vertical or horizontal line, they could just ask you for the x or y ordinate cause they already tested you on the other ordinate in finding the equation of the asymptote