Help with Trig Expressions

[lewch45]

I have 2 homework problems that are very similar and I'm not sure how to go about solving them. Here they are...

(1) cot 0 = -1.90 deg < theta < 180 deg; find cos 0


(2) tan 0 = 1 and sin 0 <0; find cos 0

I know I'm supposed to evaluate what Quadrant they're in (for #2 it's Quadrant 3) but I'm not sure what to do from there. Can anyone help please?

 

[Daniel_Feldman]

I have 2 homework problems that are very similar and I'm not sure how to go about solving them. Here they are...

(1) cot 0 = -1.90 deg < theta < 180 deg; find cos 0

Do you mean cot(theta)=-1?


(2) tan 0 = 1 and sin 0 <0; find cos 0

I know I'm supposed to evaluate what Quadrant they're in (for #2 it's Quadrant 3) but I'm not sure what to do from there. Can anyone help please?

 

[galactus]

Is that 0 supposed to be a theta\(\displaystyle {\theta}\), as in cos 0 is actually \(\displaystyle cos

{\theta}\)?. You're not going to get a response if folks must try to interpret
such things.

I will use degrees for this. For #2, it is quadrant 3 because tan(225)

=1, sin(225)=\(\displaystyle \frac{-sqrt{2}}{2}\), which is <0. So, cos(225)=\(\displaystyle \frac

{-sqrt{2}}{2}\).

For the first one, cot(0)=-1.90<theta<180 makes no sense. Maybe I can translate.

I assume Daniel is correct?. \(\displaystyle cot{\theta}=-1\),\(\displaystyle 90<{\theta}<180\)

What \(\displaystyle {\theta}\) makes cot equal -1?. It must be between 90 and 180 degrees, so that whittles it down. Hint: cot(45)=1 and cot(225)=1.

Please, try to post accurate statements. I know sometimes it seems like we're all-seeing and all-knowing, but, alas, we are just mere mortals on the other side of the computer screen. :wink:

 

[lewch45]

yep...didn't know how to write it.

cot (theta) = -1.90 deg < theta < 180 deg; find cos (theta)

 

[galactus]

That looks like cot(theta) is between -1.90 degrees and 180 degrees. I know that isn't what you mean.