Given:
2tan−1(cosx)=tan−1(2 cosec x)
{2tan−1x=tan−12x1−x2}
⇒tan−12cosx1−cos2x=tan−1(2 cosec x)
⇒tan−1(2cosxsin2x)=tan−1(2 cosec x)
⇒2cosxsin2x=2 cosec x
⇒cosxsin2x= cosec x
⇒cosxsin2x=1sinx
⇒cosx=sin2xsinx
⇒cosx=sinx
⇒1=sinxcosx
⇒tanx=1
⇒tanx=tanπ4
⇒x=nπ+π4,n∈Z
Hence, the value of x is nπ+π4,n∈Z.