If x, y are positive integers and tan−1x+cos−1y√1+y2=sin−13√10 then number of ordered pairs of (x, y) is:
A
infinitely many
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B
one
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C
two
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D
\N
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Solution
The correct option is C two Since y > 0 given equation can be re-written as tan−1x+tan−11y=tan−13⇒x+(1y)1−(xy)=3⇒xy+1=3y−3x⇒y=3x+13−x
Since x and y are positive integers, x=1⇒y=2,x=2⇒y=7.
Hence ordered pairs (x, y) = (1, 2), (2, 7)