Eliminate the Intruder!
If θ is eliminated from the equations x = a cos ( θ − α ) and y = b cos ( θ − β ) , which of the following is the resulting equation obtained?
- a 2 x 2 + b 2 y 2 + a b 2 x y cos ( α − β ) = cot 2 ( α − β )
- a 2 x 2 + b 2 y 2 − a b 2 x y cos ( α − β ) = sin 2 ( α − β )
- a 2 x 2 − b 2 y 2 + a b 2 x y cos ( α − β ) = tan 2 ( α − β )
- a 2 x 2 − b 2 y 2 − a b 2 x y cos ( α − β ) = − csc 2 ( α − β )
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1 solution
Yeah, the problem does become easy in an objective type paper. However, in subjective type(which I sincerely hope is not the case, but JEE might be in the coming years), this may prove out to be tough question.
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I just put α , β = 0 .So the option is 2.But there is also a simple solution for subjective paper
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Can you pls post a subjective solution also??
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@Pranav Saxena – Sorry..I can't it will take a lot of time to latex.But this was already done in our class
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@Spandan Senapati – Well, an image would do...
I Did objective way
first let theta =alpha= beta
This eliminates 1,4
Then let alpha = 0 , beta = theta = pi/2
This eliminates 3
Hence answer is 2 and this problem can be solved under a minute in any competitive exam this way