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Mathematics 15 Online
OpenStudy (anonymous):

Express sin(-113 degree) as the function of a positive acute angle less than 45 degree

OpenStudy (jdoe0001):

on which quadrant do you think the angle \(-113^o\) is at?

OpenStudy (anonymous):

3rd quadrant

OpenStudy (jdoe0001):

ok, if you were to go counterclockwise, or 'positive' movement, where would the \(113^o\) would be at? II quadrant, well, what you're after is its SUPPLEMENTARY angle

OpenStudy (anonymous):

67 degree ???

OpenStudy (jdoe0001):

yes, \(67^o\) on the II quadrant, where SINE is positive

OpenStudy (jdoe0001):

and 67 is also acute

OpenStudy (anonymous):

but the answers are 1) sin 57 2) cos 23 3) -cos 23 4) csc 23

OpenStudy (jdoe0001):

ohh, it has to be less than 45, ok

OpenStudy (anonymous):

that's why i'm confusing :D

OpenStudy (anonymous):

do you have any idea?

OpenStudy (jdoe0001):

no yet :|

OpenStudy (anonymous):

i typed in my calculator and i found that -cos23 is equal to sin(-113)

OpenStudy (jdoe0001):

right, it has to be it's counterpart in the internal angles, cos(23)

OpenStudy (jdoe0001):

the sin(60) = cos(30), becuase THE SAME line makes 60degrees from the origin, AND 30degrees from the arc, and those internal angles are usually a cos/sin relation

OpenStudy (anonymous):

|dw:1367708552997:dw|it looks like this right ?

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