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Grade 10Trigonometry

Sir please gave the proof. cos^4x + sin^4x = 1- 2 cos^2x sin^2x.

Profile image of Manish Raheja
9 Years agoGrade 10
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2 Answers

Profile image of sanad
9 Years ago
L.H.S
Profile image of sanad
9 Years ago
L.H.S
= sin4x  +cos4x
It  can  be  writen  in  this   way
= (sin2x)2  +  cos4x
= ( 1 – cos2x)2  +  cos4x
= 1 +cos4x – 2cos2x + cos4x
= 1 – 2cos2x +2 cos4x
=1 – 2cos2x(1 – cos2x)
= 1 – 2cos2xsin2x  
 

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