If sin−1x+sin−1y=π2, then 1+x4+y4x2−x2y2+y2is equal to
1
2
12
None of these
sin−1x+sin−1y=π2⇒sin−1x=π2−sin−1y=cos-1y
⇒sin−1x=sin−11−y2⇒x=1-y2⇒x2+y2=1∴1+x4+y4x2−x2y2+y2=1+(x2+y2)2−2x2y21−x2y2
=1+1−2x2y21−x2y2 =2