UTpaper

Free mock tests & test series

Question 3Asked in DSSSB TGT Computer Science (Technical), 1 Aug 2021, Shift 3

If x + iy = tan(A + iB), then what is the value of x² + y² + 2x cot 2A − 2?

  1. A1
  2. B−1
  3. C0
  4. D2
Show answerHide answer

Correct answer: (B) −1

Explanation

tan(A+iB) + tan(A−iB) = 2x and tan(A+iB)·tan(A−iB) = x² + y², so tan 2A = 2x/(1 − x² − y²), i.e. x² + y² + 2x cot 2A = 1. Subtracting 2 gives −1.

From DSSSB TGT Computer Science PYQ (Technical), 1 Aug 2021, Shift 3

This is question 3 of DSSSB TGT Computer Science PYQ (Technical), 1 Aug 2021, Shift 3. See all questions of this paper with answers, or attempt the paper as a timed online test to get your score and all-India rank.