If ∫ 0 π / 3 tan ⁡ θ 2 k   sec ⁡ θ d θ = 1 - 1 2 ,   ( k…

If 0π/3tanθ2ksecθdθ=1-12, (k>0) , then the value of k is
  1. 12
  2. 1
  3. 2
  4. 4

Solution

0π/3tanx2ksecxdx

=12k 0π/3sinxcosxdx

Put t=cosx

dt= -sinx dx, also x=0, t=1;x=π3, t=12

  12k 11/2-dtt

=12k1/21t-12 dt=12k×2 t121/21 

=2k 1-12=2-1k

Given 2-1k=1-12=2-12

k=2

Asked in: JEE Main 2019 (09 Jan Shift 2)

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