Posted by **Purplechick4** on Monday, February 6, 2012 at 9:28pm.

find the exact value of sin(-15pi/6) and cot(-7pi/6)

- Pre-Calc -
**Reiny**, Monday, February 6, 2012 at 10:00pm
Perhaps you can "think" better in degrees than radians, sometimes I can.

sin(-15π/6)

= sin(-450°)

= sin(-90) , I took away one rotation

= -sin(90°) = -1

cot (-7π/6)

= cot(-210°)

= cot(150°) , 150 and -210 are coterminal

= - cot(30°) , 150 is in II and by CAST rule cotangent is negative, and 30° from the x-axis

= -1/tan 30°

= -1/(1/√3) = -√3

- Pre-Calc -
**Purplechick4**, Monday, February 6, 2012 at 10:09pm
Thank youu(:

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