The number of solution of tanx+secx=2cosx in [0,2π] is
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Solution
We can simplify the equation by converting everything to sines and cosines: cosxsinx+cosx1=2cosx Multiplying through by cosx gives: sinx+1=2cos2x Using the identity cos2x+sin2x=1, we can substitute sin2x with 1−cos2x to get: sinx+1=2−2sin2x Rearranging terms gives: 2sin2x+sinx−1=0 This is a quadratic equation in sinx, which we can solve using the quadratic formula: sinx=4−1±1+8 The discriminant is positive, so there are two solutions for sinx: sinx=4−1±9=−1,21 For sinx=−1, we have x=23π. For sinx=21, we have x=6π,65π. Therefore, there are a total of 3 solutions in the interval [0,2π].