trigno

Q
If
\frac{cos^{4}x}{cos^{2}y}+\frac{sin^{4}x}{sin^{2}y}=1

Then prove that

\frac{cos^{4}y}{cos^{2}x}+\frac{sin^{4}y}{sin^{2}x}=1

2 Answers

isko to koi bata do[2]

look manipal ....

write sin²a as 1 - cos²a in ur first equation....

ur expression simplifies to

cos⁴x - 2cos²x.cos²y + cos⁴y = 0

this is

( cos²x - cos²y ) = 0

cos²x = cos²y and sin²x = sin²y !!

So, the second eqⁿ follows ...

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