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Prove that the determinant |xsinθcosθ-sinθ-x1cosθ1x| is independent of θ. - Mathematics

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प्रश्न

Prove that the determinant `|(x,sin theta, cos theta),(-sin theta, -x, 1),(cos theta, 1, x)|` is independent of θ.

योग

उत्तर

Let, Δ = `[(x,sintheta,costheta),(-sintheta,-x,1),(costheta,1,x)]`

= x(-x2 - 1) - sin θ (-xsin θ - cos θ) + cos θ(-sin θ + xcosθ)

= -x(x2 + 1) + xsin2θ + sinθcosθ - sinθcosθ + xcos2θ

= -x(x2 + 1) + x (sin2θ + cos2θ)

= -x(x2 + 1) + x = -x[x2 + 1 - 1]

= -x3

which is independent of θ.

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अध्याय 4: Determinants - Exercise 4.7 [पृष्ठ १४१]

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एनसीईआरटी Mathematics [English] Class 12
अध्याय 4 Determinants
Exercise 4.7 | Q 1 | पृष्ठ १४१

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