Composition of Trigonometric Functions and Inverse Trigonometric Functions
tan -1x/y-tan...
Question
tan−1(xy)−tan−1(x−yx+y) is equal to a) π2 b) π3 c) π4 d) −3π4
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Solution
tan−1(xy)−tan−1(x−yx+y)=tan−1(xy)−tan−1(xy−1xy+1)=tan−1(xy)−{tan−1xy−tan−11}[∵tan−1x−tan−1y=tan−1(x−y1+xy)] =tan−11=π4, Hence, the correct option is (c).