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Mathematics 16 Online
OpenStudy (anonymous):

True or False: 1. the tangent increases in the third quadrant 2. the cosecant increases in the third and fourth quadrant 3. the sine increases in the third quadrant 4. the sine function is odd 5. the secant function is odd 6. in the first quadrant all six functions are positive 7. the sin 20 is less than the sin 25 8. the tan 45 is 1 9. the tangent is positive in the third and fourth quadrant 10. the tan 24 is less than tan 35 11. the greatest value of secant is 1 12. the cotangent function is odd 13. if the tangent is negative then the cotangent is negative

OpenStudy (anonymous):

@Hero

OpenStudy (anonymous):

@jim_thompson5910

OpenStudy (anonymous):

thanks?

OpenStudy (anonymous):

Many of these can be reasoned through with the help of a unit circle.

jimthompson5910 (jim_thompson5910):

here is the unit circle |dw:1353799039860:dw|

jimthompson5910 (jim_thompson5910):

Quadrant III is in the lower left corner

OpenStudy (anonymous):

i dont get the ones that talk about sin cos tan increasing and decreasing?? :\ ...i know the unit circle and the quadrants

jimthompson5910 (jim_thompson5910):

as the angle increases, a) sine increases or b) sine decreases

OpenStudy (anonymous):

b?

jimthompson5910 (jim_thompson5910):

yes, since tan = sin/cos, tangent also decreases in Q3

OpenStudy (anonymous):

wait but can you explain how exactly the sin decreases?

jimthompson5910 (jim_thompson5910):

oh wait, i'm not counting cosine here as the angle increases, cosine also decreases in Q3

OpenStudy (anonymous):

Also useful: http://www.sparknotes.com/math/trigonometry/graphs/section2.rhtml

jimthompson5910 (jim_thompson5910):

oops cosine increases here i meant

OpenStudy (anonymous):

how exactly do they "increase/decrease" ??

jimthompson5910 (jim_thompson5910):

here is one angle |dw:1353799316535:dw|

jimthompson5910 (jim_thompson5910):

here is the tangent of that angle |dw:1353799347459:dw|

jimthompson5910 (jim_thompson5910):

increase the angle to get this new angle |dw:1353799399641:dw|

jimthompson5910 (jim_thompson5910):

the tangent of that angle is |dw:1353799413973:dw|

OpenStudy (anonymous):

|dw:1353799407499:dw|

jimthompson5910 (jim_thompson5910):

you can see that the lengths of the tangent segments are getting longer, which means that tangent is increasing as the angle increases in Q3

jimthompson5910 (jim_thompson5910):

no in Q2, sine is decreasing

jimthompson5910 (jim_thompson5910):

same with Q3

OpenStudy (anonymous):

how?

jimthompson5910 (jim_thompson5910):

sine is just the y coordinate of the point on the unit circle

OpenStudy (anonymous):

okay i know tan=slope sin=y cos=x

jimthompson5910 (jim_thompson5910):

in Q2 and Q3, the y coordinates are decreasing

OpenStudy (anonymous):

no, the x coordinates are decreasing..?

jimthompson5910 (jim_thompson5910):

yeah and tan = length of tangent segment that starts at the terminal point and it intersects the x axis

jimthompson5910 (jim_thompson5910):

in Q2, the x coordinates decrease, in Q3, the x coordinates increase

OpenStudy (anonymous):

|dw:1353799588030:dw|right?

jimthompson5910 (jim_thompson5910):

right

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