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  1. If x cosθ – sinθ = 1, then x² + (1 +x² ) sinq equals
    1. 2
    2. 1
    3. - 1
    4. 0
Correct Option: B

x cosθ – sinθ = 1
⇒ x cosθ = 1 + sinθ

⇒ x =
1
+
sin θ
cos θcos θ

⇒ x = secθ + tanθ --- (i)
∵ sec²θ – tan²θ = 1
⇒ (secθ + tanθ) (secθ – tanθ) =1
⇒ secθ – tanθ =
1
(ii)
x

From equation (i) + (ii),
2secθ = x +
1
=
x² + 1
xx

⇒ secθ =
x² + 1
2x

From equation (i) – (ii),
2tanθ = x –
1
=
x² - 1
xx

∴ tanθ =
x² - 1
2x

∴ sinθ =
tanθ
secθ

=
x² - 1
×
2x
=
x² - 1

2xx² + 1x² + 1

∴ Expression = x² – (1 + x² ) sinθ
= x² - (1 + x²) ×
x² - 1
= x² - x² + 1 = 1
x² + 1

Note : In the original equation x² + (1 + x² ) sinθ has been given that seems incorrect



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