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what is the value of  cos 135

   

cos135=cos(90+45)

  =  -cos 45  =  -1/underoot 2

cos is -ve in 2nd quad and where cos deos not  change to sin

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cos 135

=cos(180-45)

=cos 45

=-1/root2

cos is negative in the second quadrant and as i have used 180 degree cos will not change into sin

if i had used 90 degree cos changes into sin 

  • -1

cos(135)

=cos(90+45)

= -sin(45) 

= -(1/root2)

= -1/root2

  • 4

-1/root2

  • 1

cos(180-45)
-cos45
-1/root2

  • 1
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