# quick help with quadrants

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• Apr 25th 2010, 02:09 PM
d1338
quick help with quadrants
i have a problem that is:

directions:
"Let theta be an angle in standard position. In which quadrant or quadrants can theta lie under the given conditions?"

Sin theta and tan theta have the same sign.

Can someone who answers this also explain how to do this problem? I have a unit circle graph but have no idea how to use it.... ty in advance
• Apr 25th 2010, 02:25 PM
Archie Meade
Quote:

Originally Posted by d1338
i have a problem that is:

directions:
"Let theta be an angle in standard position. In which quadrant or quadrants can theta lie under the given conditions?"

Sin theta and tan theta have the same sign.

Can someone who answers this also explain how to do this problem? I have a unit circle graph but have no idea how to use it.... ty in advance

Hi d1338,

$\displaystyle tan\theta=\frac{sin\theta}{cos\theta}$

hence, an easy way to look at this is....

$\displaystyle sin\theta$ and $\displaystyle tan\theta$ have the same sign only when $\displaystyle cos\theta$ is positive.

Hence, you need to know where $\displaystyle cos\theta$ is positive, which occurs for angles to the right of the y-axis.
• Apr 25th 2010, 02:27 PM
skeeter
Quote:

Originally Posted by d1338
i have a problem that is:

directions:
"Let theta be an angle in standard position. In which quadrant or quadrants can theta lie under the given conditions?"

Sin theta and tan theta have the same sign.

Can someone who answers this also explain how to do this problem? I have a unit circle graph but have no idea how to use it.... ty in advance

quad I ... sin and cos both (+)

quad II ... sin(+) , cos(-)

quad III ... sin and cos both (-)

quad IV ... sin(-), cos(+)

note that tangent is the ratio of sine/cosine
• Apr 25th 2010, 03:19 PM
harish21
Quote:

Originally Posted by d1338
i have a problem that is:

directions:
"Let theta be an angle in standard position. In which quadrant or quadrants can theta lie under the given conditions?"

Sin theta and tan theta have the same sign.

Can someone who answers this also explain how to do this problem? I have a unit circle graph but have no idea how to use it.... ty in advance

This is how I learnt:
Remember ASTC : Add Sugar To Coffee

A: 1st quadrant: All identities are positive
S: 2nd quadrant: only sine is positive
T: 3rd quadrant: only tan is positive
C: 4th quadrant: only cosine is positive
• Apr 26th 2010, 07:17 AM
kandyfloss
All silver tea cups