If secθ=m and tanθ=n, then 1mm+n+1m+n is equals to
2
2m
2n
mn
Explanation for the correct option
Substitute the value of secθ=m and tanθ=n in 1m[(m+n)+1(m+n)], then
1m[(m+n)+1(m+n)]=1secθsecθ+tanθ+1secθ+tanθ=1secθsec2θ+tan2θ+2tanθsecθ+1secθ+tanθ
Put trigonometry identity tan2(θ)=sec2(θ)-1
1m[(m+n)+1(m+n)]=1secθsec2θ+sec2θ-1+2tanθsecθ+1secθ+tanθ=2sec2θ+2secθtanθsecθsecθ+tanθ
Take common 2secθ in the numerator,
1m[(m+n)+1(m+n)]=2secθsecθ+tanθsecθsecθ+tanθ=2
The value of 1mm+n+1m+n is equal to 2
Hence, option A is correct.
loge(n+1)−loge(n−1)=4a[(1n)+(13n3)+(15n5)+...∞] Find 8a.