Prove that  from Class 12 CBSE Previous Year Board Papers | Ma

Subject

Mathematics

Class

CBSE Class 12

Pre Boards

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Sample Papers

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 Multiple Choice QuestionsShort Answer Type

1.

If A is a 3 × 3 invertible matrix, then what will be the value of k if det(A–1) = (det A)k.

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2.

Determine the value of the constant ‘k’ so that the function  is continuous at x = 0.

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3.

If a line makes angles 90° and 60° respectively with the positive directions of x and y axes, find the angle which it makes with the positive direction of the z-axis.

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4.

Show that all the diagonal elements of a skew symmetric matrix are zero.

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5.
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6.

The volume of a sphere is increasing at the rate of 3 cubic centimetres per second. Find the rate of increase of its surface area, when the radius is 2 cm.

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7.

Show that the function f(x) = 4x3 – 18x2 + 27x – 7 is always increasing on R.

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8.

Prove that 


Let space cos to the power of negative 1 end exponent space equals space open parentheses straight a over straight b close parentheses space equals space straight x
Then comma space cos space straight x space equals space straight a over straight b
LHS colon
tan open curly brackets straight pi over 4 plus 1 half cos to the power of negative 1 end exponent straight a over straight b close curly brackets plus space tan space open parentheses straight pi over 4 minus 1 half cos to the power of negative 1 end exponent straight a over straight b close parentheses
equals space tan open parentheses straight pi over 4 space plus straight x over 2 close parentheses plus space tan space open parentheses straight pi over 4 minus straight x over 2 close parentheses
fraction numerator 1 plus space tan begin display style straight x over 2 end style over denominator 1 minus tan begin display style straight x over 2 end style end fraction space plus fraction numerator 1 minus space tan begin display style straight x over 2 end style over denominator 1 plus tan begin display style straight x over 2 end style end fraction
fraction numerator open parentheses 1 plus tan begin display style straight x over 2 end style close parentheses squared plus open parentheses 1 minus tan begin display style straight x over 2 end style close parentheses squared over denominator 1 minus tan squared begin display style straight x over 2 end style end fraction
space equals space 2 open parentheses fraction numerator 1 plus tan squared begin display style straight x over 2 end style over denominator 1 minus tan squared begin display style straight x over 2 end style end fraction close parentheses
space equals space fraction numerator 2 over denominator cos space straight x end fraction space open square brackets because space cos space 2 straight x space equals space fraction numerator 1 minus tan squared straight x over denominator 1 plus space tan squared space straight x end fraction close square brackets
space equals space fraction numerator 2 straight b over denominator straight a end fraction space equals space RHS
Hence space proved
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9.

Using properties of determinants, prove that 

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10.

Let find a matrix D such that CD – AB = O.

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