Maths help

ted9308

Anyone care to help me solve the following? Lim(x-0) sinxtanx/x^2???I have reduced tan x to sinx/cosx giving me sin^2x/cosx//x^2 ..have then attempted to find the limit of sin^2x and 1/cosx//x2 and have multiplied them only to get the answer wrong..?

Maybe_Memories

ted9308 wrote: »

Anyone care to help me solve the following? Lim(x-0) sinxtanx/x^2???I have reduced tan x to sinx/cosx giving me sin^2x/cosx//x^2 ..have then attempted to find the limit of sin^2x and 1/cosx//x2 and have multiplied them only to get the answer wrong..?

Have you studied L'Hopital's Rule?

MathsManiac

All these kinds of questions on the LC course can be handled using the fact that the limit as x->0 of [sin(x)]/x is 1.

In this case, group your expression as [sin(x)]/x times [sin(x)]/x times 1/cos(x), and apply the product rule for limits.

(L'Hopital's rule is not on the LC course, so most students wouldn't know it at this level.)

Maybe_Memories

MathsManiac wrote: »

All these kinds of questions on the LC course can be handled using the fact that the limit as x->0 of [sin(x)]/x is 1.

In this case, group your expression as [sin(x)]/x times [sin(x)]/x times 1/cos(x), and apply the product rule for limits.

(L'Hopital's rule is not on the LC course, so most students wouldn't know it at this level.)

Ah right, sorry. I did see it in a revision book a few years ago though

MathsManiac

Maybe_Memories wrote: »

Ah right, sorry. I did see it in a revision book a few years ago though

Yeah, some do it, but I'm not sure whether it's "allowed".