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What are the coordinates of the point that corresponds to −7π on the unit circle?

 

(−2√2, 2√2)

(2√2, −2√2)

(2√2, 2√2)

(−2√2, −2√2)

 

Let cos(−θ)=−35cos(−θ)=−35 and  tanθ>0 .

What is the value of sin(−θ)?

 

4/3

−3/5

4/5

−4/5

 Jan 16, 2018
 #1
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-7 pi    is the same angle as  + pi ......  on the unit circle, the coordinates  are  (-1, 0)

 

 

 

cos(−θ) =−3/5       tan θ  > 0  

 

Note  that  cos(-θ) = cos (θ)  ....so....this angle is is in the 3rd quadrant.......so....the sin (-θ) is

 

y / r  =   - √ [5^2  - (-3)^2 ]  / 5   =  - √ 16/ 5   =   - 4 / 5

 

 

cool cool cool

 Jan 16, 2018

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