Parametric and Remembering Formula (1 Viewer)

[frog1944]

Hi,

We've started parametrics and there is a nice formula for finding the equation of a tangent at a point (xx_0 = 2a(y+y_1)) on a parabola. Are we allowed to just use this equation in a question? Or would we have to prove it?
My teacher says if we wanted to use it in a question asking to find the equation of the tangent at a point on the parabola, we would need to prove it, then use it (or he said we could do it the normal way).
I don't see why we can't use this, isn't it part of the syllabus? Isn't it like saying here is the compound angle formulae for the trigonometric functions, but you can't use them unless you prove them in the test.

Thanks

 

[Paradoxica]

Hi,

We've started parametrics and there is a nice formula for finding the equation of a tangent at a point (xx_0 = 2a(y+y_1)) on a parabola. Are we allowed to just use this equation in a question? Or would we have to prove it?
My teacher says if we wanted to use it in a question asking to find the equation of the tangent at a point on the parabola, we would need to prove it, then use it (or he said we could do it the normal way).
I don't see why we can't use this, isn't it part of the syllabus? Isn't it like saying here is the compound angle formulae for the trigonometric functions, but you can't use them unless you prove them in the test.

Thanks

I think this is on the formula sheet so you can quote it. "Reference sheet"

 

[leehuan]

Hi,

We've started parametrics and there is a nice formula for finding the equation of a tangent at a point (xx_0 = 2a(y+y_1)) on a parabola. Are we allowed to just use this equation in a question? Or would we have to prove it?
My teacher says if we wanted to use it in a question asking to find the equation of the tangent at a point on the parabola, we would need to prove it, then use it (or he said we could do it the normal way).
I don't see why we can't use this, isn't it part of the syllabus? Isn't it like saying here is the compound angle formulae for the trigonometric functions, but you can't use them unless you prove them in the test.

Thanks

It used to not be a 'formula' to be quoted unlike compound angles. You had to derive it unless they smack bang gave it in front of you.

But now it's fine.

 

[frog1944]

Ok, how do you know if you can quote a result or formula? Will it tell you in the syllabus?