Q28 / 54 · JEE Advanced 2020 (Paper 1) · Mathematics

Let x, y and z be positive real numbers. Suppose x, y and z are the lengths of the sides of a triangle opposite to its angles X, Y and Z  respectively. If tanX2+tanZ2=2yx+y+z, then which of the following statements is/are TRUE?

  • A
    2Y=X+Z
  • Correct answer
    B
    Y=X+Z
  • Correct answer
    C
    tanX2=xy+z
  • D
    x2+z2−y2=xz

Solution

We have, tanX2+tanZ2=2yx+y+z & s=x+y+z=perimeter of a triangle  

Apply half-angle formula and x+y+z=s then, 

⇒∆ss−x+∆ss−z=ys⇒∆=s−xs−z

⇒∆2=ss−xs−ys−z=s−x2s−z2

⇒y2=x2+z2⇒∠Y=90°

⇒∠Y=∠X+∠Z

An option B is correct.

Now, xy+z=sinXsinY+sinZ=sinX1+sinπ2-X=2sinX2cosX22cos2X2=tanX2

An Option C is correct.

Hence, the correct answer is options: 'B', 'C'.

Relevant Questions