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Mathematics

1sin Acos A\dfrac{1 - \text{sin A}}{\text{cos A}} = sec A - tan A

Statement (1): 1sin Acos A\dfrac{1 - \text{sin A}}{\text{cos A}} = sec A - tan A

1+sin Acos A\Rightarrow \dfrac{1 + \text{sin A}}{\text{cos A}} = sec A + tan A

Statement (2): 1sin Acos A1+sin Acos A\dfrac{1 - \text{sin A}}{\text{cos A}} - \dfrac{1 + \text{sin A}}{\text{cos A}} = 2sec A

  1. Both the statements are true.

  2. Both the statements are false.

  3. Statement 1 is true, and statement 2 is false.

  4. Statement 1 is false, and statement 2 is true.

Trigonometric Identities

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Answer

Given, 1sin Acos A\dfrac{1 - \text{sin A}}{\text{cos A}} = sec A - tan A

Taking L.H.S.

1sin Acos A1cos Asin Acos Asec Atan A\Rightarrow \dfrac{1 - \text{sin A}}{\text{cos A}}\\[1em] \Rightarrow \dfrac{1}{\text{cos A}} - \dfrac{\text{sin A}}{\text{cos A}}\\[1em] \Rightarrow \text{sec A} - \text{tan A}

As, L.H.S. = R.H.S., so equation is true.

Now, 1+sin Acos A\dfrac{1 + \text{sin A}}{\text{cos A}} = sec A + tan A

Taking L.H.S.

1+sin Acos A1cos A+sin Acos Asec A+tan A\Rightarrow \dfrac{1 + \text{sin A}}{\text{cos A}}\\[1em] \Rightarrow \dfrac{1}{\text{cos A}} + \dfrac{\text{sin A}}{\text{cos A}}\\[1em] \Rightarrow \text{sec A} + \text{tan A}

As, L.H.S. = R.H.S., so equation is true.

So, statement 1 is true.

Now, 1sin Acos A1+sin Acos A\dfrac{1 - \text{sin A}}{\text{cos A}} - \dfrac{1 + \text{sin A}}{\text{cos A}} = 2sec A

Solving L.H.S.

1sin Acos A1+sin Acos A\Rightarrow \dfrac{1 - \text{sin A}}{\text{cos A}} - \dfrac{1 + \text{sin A}}{\text{cos A}}

1cos Asin Acos A(1cos A+sin Acos A)\Rightarrow \dfrac{1}{\text{cos A}} - \dfrac{\text{sin A}}{\text{cos A}} - \Big(\dfrac{1}{\text{cos A}} + \dfrac{\text{sin A}}{\text{cos A}}\Big)

⇒ (sec A - tan A) - (sec A + tan A)

⇒ sec A - tan A - sec A - tan A

⇒ -2tan A.

As, L.H.S. ≠ R.H.S.

So, statement 2 is false.

∴ Statement 1 is true and statement 2 is false.

Hence, option 3 is the correct option.

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