Posted by **Jake** on Sunday, June 6, 2010 at 9:36pm.

Regarding the trigonometric series,

Why does cos start with a 1 and why are the powers of x even numbers

Also for sin, why does sin start with an x and why are the powers odd?

- trig -
**Reiny**, Sunday, June 6, 2010 at 9:48pm
You must be referring to the expansion so sinx and cosx

sinx = x - x^3/3! + x^5/5! - x^7/7! + ... and

cosx = 1 - x^2/2! + x^4/4! - x^6/6! ...

I don't know if you have learned about the Taylor Series expansion.

Here is a page that develops the sinx expansion

http://www.intmath.com/Series-expansion/2_Maclaurin-series.php

- trig -
**MathMate**, Monday, June 7, 2010 at 7:57am
The above reference should help you to answer the questions:

Why does cos start with a 1 and why are the powers of x even numbers

- think of what cos(0) equals, and

- is cos(x) an even or odd function?

Also for sin, why does sin start with an x and why are the powers odd?

- Evaluate lim sin(x)/x as x->0

- Is sin(x) an even or odd function?

## Answer this Question

## Related Questions

- TRIG! - Posted by hayden on Monday, February 23, 2009 at 4:05pm. sin^6 x + cos^6...
- Mathematics - Trigonometric Identities - Let y represent theta Prove: 1 + 1/tan^...
- math - Prove that for all real values of a, b, t (theta): (a * cos t + b * sin t...
- trig - Reduce the following to the sine or cosine of one angle: (i) sin145*cos75...
- tigonometry - expres the following as sums and differences of sines or cosines ...
- Trigonometry - I have some trigonometric equations to do, but I'm pretty lost, ...
- Math - Calculus - The identity below is significant because it relates 3 ...
- algebra - Can someone please help me do this problem? That would be great! ...
- Alg2/Trig - Find the exact value of the trigonometric function given that sin u...
- MathsSs triG - Consider sin(x-360)sin(90-x)tan(-x)/cos(90+x) 1.A.SIMPLIFY sin(x-...