tan−1[3sin2α5+3cos2α]+tan−1[tanα4]=λα4 where −π2<α<π2, then λ is ___.
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tan−1[3sin2α5+3cos2α]+tan−1[tanα4]=tan−1(6tanα8+2tan2α)+tan−1(tanα4)(∵3tan2α16+4tan2α<1)=tan−1(tanα)=α