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Mathematics 20 Online
OpenStudy (darkbluechocobo):

Help with trig Identities

OpenStudy (darkbluechocobo):

\[\tan \theta= -2 and \sin \theta<0, find \sec \theta \]

OpenStudy (campbell_st):

ok... so \[\tan(\theta) = -2\] and \[\sin(\theta) < 0\] so which quadrant of the unit circle has both sin and tan negative |dw:1421698552342:dw|

OpenStudy (darkbluechocobo):

three?

OpenStudy (freckles):

tan=sin/cos=negative in this case if we know sin=negative then cos is ?

OpenStudy (freckles):

recall (-)/(-)=+ (-)/(+)=- (+)/(-)=- (+)/(+)=+

OpenStudy (freckles):

we can only consider the two middle ones there since our quotient is negative (-)/(+)=- (+)/(-)=-

OpenStudy (darkbluechocobo):

positiive if two are negatives

OpenStudy (freckles):

and we know sin is neg so we have (-)/(+)=-

OpenStudy (freckles):

but we are given tan is negative not positive

OpenStudy (darkbluechocobo):

-=-/+

OpenStudy (freckles):

so cosine has to be positive right?

OpenStudy (freckles):

|dw:1421699174829:dw|

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