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vishwa sharma Grade: 10
        

if sinx+sin2x=2


then find,cos2x+cos4x

7 years ago

Answers : (2)

Vinay Arya
37 Points
										

Hi Vishwa Sharma

sinx+sin2x=2

=>sinx+sin2x-2=0

=>(sinx-1)(sinx+2)=0

=>sinx=1 or sinx=-2

 We know that sinx cannot be equal to -2.Hence rejaecting sinx=-2

 Therefore, sinx=1 =>x=pi/2

  cos2x+cos4x=xos2pi/2 + cos4pi/2 =0

 

7 years ago
Chaitanya Borah
34 Points
										

sinx+sin2x=2

=>sinx=1+1-sin2x

=>sinx=1+cos2x

=>cos2x=sinx-1

now,

cos2x+cos4x

=cos2x+(sinx-1)2

=cos2x+sin2x-2sinx+1

=1-2sinx+1

=2(1-sinx)

7 years ago
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