Which of the following is a FALSE statement?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is Option 1 i.e. tan2 A = 1 - sec2 A.
Option 1: tan2A = 1 - sec2A
Solving R.H.S
⇒ 1 - sec2A
⇒ 1 - 1/cos2A
⇒ (cos2A - 1)/cos2A
⇒ -sin2A/cos2A = -tan2A
Option 2: sinA = tanA × cosA
Solving R.H.S
⇒ tanA × cosA = sinA/cosA × cosA = sinA
Option 3: cosec2A - 1 = cot2A
Solving L.H.S
⇒ cosec2A - 1 = 1/sin2A - 1
⇒ (1 - sin2A)/sin2A
⇒ cos2A/sin2A = tan2A
Option 4: cosA × secA = 1
⇒ Solving L.H.S
⇒ cosA × secA = 1/secA × secA = 1
Thus, only Option 1 is incorrect