Rachel E.

asked • 02/23/17

If x=arctan(-3/4) and x+y=210 degrees, then cosy=?

If x=arctan(-3/4) and x+y=210 degrees, then cosy=? (Estimate answer to two decimal places).

1 Expert Answer

By:

Michael J. answered • 02/23/17

Understanding all Sines of Triangles

arctan(-3/4) means to find the angle x that makes tanx=-3/4.  Knowing that,
 
cosy = cos[210 - arctan(-3/4)]
 
 
Use the calculator to find the estimation.
 
 
 
 
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