trig identities..

[alohadressage]

i cant remember what these are called, but you know that formula where like, if (x^2+y^2)^1/2=r^2, then sin=x/r, cos=y/r, or something like that? well, i cant remember what sin, cos, tan, cosec, sec, and cot equal...can anyone please tell me?
: ] thanks...

 

[stapel]

i cant remember what these are called, but you know that formula where like, if (x^2+y^2)^1/2=r^2, then sin=x/r, cos=y/r, or something like that? well, i cant remember what sin, cos, tan, cosec, sec, and cot equal...can anyone please tell me?

I think you may be referring to the Pythagorean Theorem, and to the ratio-based definitions of the trigonometric functions...?

Any trigonometry text will cover this material near the beginning of the book. You could also try doing an online search, using the trig ratios as your keywords.

Eliz.

 

[alohadressage]

uhm no i'm not, i'm talking about something different..but thanks anyway. :]

 

[galactus]

Are you talking about converting from rectangular to polar coordinates?.

Where \(\displaystyle x=rcos{\theta}, \;\ y=rsin{\theta}, \;\ r=\sqrt{x^{2}+y^{2}}\)

 

[stapel]

i'm talking about something different.

Okay... Then what are you talking about?

Please be specific. Thank you!

Eliz.

 

[skeeter]

i cant remember what these are called, but you know that formula where like, if (x^2+y^2)^1/2=r^2, then sin=x/r, cos=y/r, or something like that? well, i cant remember what sin, cos, tan, cosec, sec, and cot equal...can anyone please tell me?
: ] thanks...

for the circle centered at the origin

\(\displaystyle x^2 + y^2 = r^2\)

the six trig ratios of the angle \(\displaystyle \theta\) in standard position whose terminal ray passes through a point on the circle are defined as ...

\(\displaystyle \cos{\theta} = \frac{x}{r}\)
\(\displaystyle \sin{\theta} = \frac{y}{r}\)
\(\displaystyle \tan{\theta} = \frac{y}{x}\)
\(\displaystyle \sec{\theta} = \frac{r}{x}\)
\(\displaystyle \csc{\theta} = \frac{r}{y}\)
\(\displaystyle \cot{\theta} = \frac{x}{y}\)

 

[galactus]

Here is something that will prove very useful in your trig travels.

The unit circle: