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The terminal ray of angle β , drawn in standard position, passes through the point (−4, 3√5) . What is the value of cosβ ? Enter your answer, in simplest radical form, in the box

 Feb 12, 2020

Best Answer 

 #1
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The point    -4 ,   3 sqrt5     forms a right triangle with the x axis     in the 2nd quadrant  ( so cos will be NEGATIVE)

   find the hypotenuse of this right triangle

 

      (-4)^2 +(3 sqrt5)^2   = hyp ^2

      16      +  45              = hyp^2

              sqrt 61   = hyp

 

 

Now   cos = adj/hyp     =    - 4 / sqrt 61       =     -4 sqrt61 / 61

 Feb 12, 2020
 #1
avatar
+1
Best Answer

The point    -4 ,   3 sqrt5     forms a right triangle with the x axis     in the 2nd quadrant  ( so cos will be NEGATIVE)

   find the hypotenuse of this right triangle

 

      (-4)^2 +(3 sqrt5)^2   = hyp ^2

      16      +  45              = hyp^2

              sqrt 61   = hyp

 

 

Now   cos = adj/hyp     =    - 4 / sqrt 61       =     -4 sqrt61 / 61

Guest Feb 12, 2020
 #2
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deleted

 Feb 12, 2020
edited by NJonah  Feb 12, 2020
edited by NJonah  Feb 12, 2020

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