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State whether the statement is True or False? Also give justification. One value of θ which satisfies the equation sin4θ - 2sin2θ - 1 lies between 0 and 2π.

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प्रश्न

State whether the statement is True or False? Also give justification.

One value of θ which satisfies the equation sin4θ - 2sin2θ - 1 lies between 0 and 2π.

विकल्प

  • True

  • False

MCQ
सत्य या असत्य
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उत्तर

This statement is False.

Explanation:

Given equation is sin4θ – 2sin2θ – 1 = 0

sin2θ = `(-(-2) +- sqrt((-2)^2 - 4 xx 1 xx -1))/(2 xx 1)`

= `(2 +-  sqrt(4 + 4))/2`

= `(2 +-  sqrt(8))/2`

= `(2 +-  2sqrt(2))/2`

= `1 +- sqrt(2)`

∴ sin2θ = `(1 + sqrt(2))` or `(1 - sqrt(2))`

⇒ – 1 ≤ sin θ ≤ 1

⇒ sin2θ ≤ 1 but sin2θ = `(1 + sqrt(2))` or `(1 - sqrt(2))`

Which is not possible.

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अध्याय 3: Trigonometric Functions - Exercise [पृष्ठ ६०]

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एनसीईआरटी एक्झांप्लर Mathematics Exemplar [English] Class 11
अध्याय 3 Trigonometric Functions
Exercise | Q 72 | पृष्ठ ६०

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