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why does sin-1(-1) = -90

Guest Apr 5, 2017
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sin-1 (-1)  = -90°

 

Note.....that  what this implies is that  sin (-90°) = -1

 

And at -90° on the unit circle, we have the point (x,y)   = (0, -1)

 

And the sine  = y / r

 

And r  = sqrt [ x ^2 + y^2 ]  =  sqrt [ 0^2 + (-1)^2 ] =  sqrt [ 1 ]  =  1

 

So  

 

sine (-90°)  =  y / r  =  -1 / 1   =    -1

 

Therefore

 

sin-1 (-1)   = -90°

 

 

 

cool cool cool

CPhill  Apr 5, 2017
edited by CPhill  Apr 5, 2017

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