Posted by **Abi** on Wednesday, February 9, 2011 at 9:59pm.

Use the graph to estimate the limit:

lim x->0 sin(3x)/x

When x is in degrees

lim x->0 sin(3x)/x = ________

I thought the the answer was (3*180)/pi but it's not... please help... Thanks

- Calculus -
**MathMate**, Wednesday, February 9, 2011 at 10:12pm
Use Lim x->0 sin(x)/x =0

The proof can be done using the sandwich (squeeze) theorem.

Expand

sin(3x)

=3cos²(x) sin(x)-sin³(x)

=sin(x)(3cos²(x)-1+(1-sin²(x)))

=sin(x)(3cos²(x)-1+cos²(x))

=sin(x)(4cos²(x)-1)

As x->0, cos(x)->1, so the limit becomes

Lim x->0 3sin(x)/x

=3 Lim x->0 sin(x)/x

The latter limit can be quoted as a standard limit, or can be proven using the sandwich theorem.

- Calculus -
**Abi**, Wednesday, February 9, 2011 at 10:18pm
The first value I tried was 3... and it didn't work either, I thought that the fact that it said "x is in degrees" affected. It also said at the end: (Give your answer accurate to at least 0.01...

- Calculus -
**MathMate**, Wednesday, February 9, 2011 at 11:33pm
Sorry, I am used to working with radians without thinking when dealing with limits and calculus. I have not properly read the instructions (would be fatal in exams!).

To change from degrees to radians, we need to multiply the number of degrees by %pi;/180, so the problem in radians is really:

Lim x->0 sin(3x*π/180)/x

=Lim x-> sin(πx/60)/x

=π/60

## Answer This Question

## Related Questions

- calculus - using the squeeze theorem, find the limit as x->0 of x*e^[8sin(1/x...
- Calculus - Can you please help me get the solution to this limit without using ...
- calculus-limits?? - i keep on doing something wrong on this problem,i guess im ...
- Calculus - yes! tnk u ok? It's actually (x->0.) Find the limit of cot(x)-csc(...
- Calculus - Use a graph to estimate: Lim x-> 0 of sin(8x)/x when x is measured...
- calculus - Lim sin2h sin3h / h^2 h-->0 how would you do this ?? i got 6 as ...
- CALCULUS LIMITS - What is the following limit? lim as n goes to infinity of (pi/...
- Calculus - What is the following limit? lim as n goes to infinity of (pi/n) (sin...
- Calculus - Find the positive integers k for which lim ->0 sin(sin(x))/x^k ...
- calc bc (condensed - is the limit as x approaches 0 of sin3x over 3x equal to ...

More Related Questions