jee-advanced

2001 mains

12 maths questions

3. Let- $1 < \mathrm { p } < 1$. Show that the equation $4 \mathrm { x } 2 - 3 \mathrm { x } - \mathrm { p } = 0$ has a unique root in the interval [1/2, 1] and identify it.
4. Let $2 \times 2 + \underset { 2 } { 2 } - 3 \times y = 0$ be the equation of a pair of tangents drawn from the origin O to a circle of radius 3 with centre in the first quadrant. If A is one of the points of contact, find the length of OA .
5. Evaluate $\int \sin - 1 ( ( 2 \mathrm { x } + 2 ) / \sqrt { } ( 4 \mathrm { x } 2 + 8 \mathrm { x } + 13 ) ) d \mathrm { x }$.
Q6 Differential equations Qualitative Analysis of DE Solutions View
6. Let $\mathrm { f } ( \mathrm { x } ) , \mathrm { x } > 0$, be a nornegative continuous function, and let $\mathrm { F } ( \mathrm { x } ) = \int 0 \mathrm { x } \mathrm { f } ( \mathrm { t } ) \mathrm { dt } , \mathrm { x } > 0$. If for some $\mathrm { c } > 0 , \mathrm { f } ( \mathrm { x } ) < \mathrm { cF } ( \mathrm { x } )$ for all $\mathrm { x } > 0$, then show that $\mathrm { f } ( \mathrm { x } ) = 0$ for all $\mathrm { x } > 0$.
7. Let $\mathrm { b } ^ { 1 } 0$ and for $\mathrm { j } = 0,1,2$, $\_\_\_\_$ n , let Sj be the area of the region bounded by the y -axis and the curve xmy $= \sin$ by, $\quad \pi / \mathrm { b } \leq \mathrm { y } \leq ( ( \mathrm { j } + 1 ) \pi ) / \mathrm { b }$.
Show that S0, S1, S2, $\_\_\_\_$ Sn are in geometric progression. Also, find their sum for $\mathrm { a } = - 1$ and $\mathrm { b } = \pi$.
Q8 Differentiation from First Principles View
8. Let $\alpha$ Î R. Prove that a function $\mathrm { f } : \mathrm { R } - - > \mathrm { R }$ is differentiable at $\alpha$ if and only if there is a function $\mathrm { g } : \mathrm { R }$ --> $R$ which is continuous at $\alpha$ and satisfies $f ( x ) - f ( \alpha ) = f ( x ) ( x - \alpha )$ for all $x \hat { I } R$.
9. Let Cl and C 2 be two circles with C 2 lying inside Cl . A circle C lying inside C1touches C1 internally and C2 externally. Identify the locus of the centre of C.
Q10 Vectors Introduction & 2D Section Ratios and Intersection via Vectors View
10. Show, by vector methods, that the angular bisectors of a triangle are concurrent and find an expression for the position vector of the point of concurrency in terms of the position vectors of the vertices.
11. (a) Let $\mathrm { a } , \mathrm { b } , \mathrm { c }$ be real numbers with $\mathrm { a } ^ { 1 } 0$ and let $\mathrm { a } , \mathrm { b }$ be the roots of the equation $\mathrm { ax } 2 + \mathrm { bx } + \mathrm { c } = 0$. Express the roots of $\mathrm { a } 2 \times 2 + \mathrm { abcx } + \mathrm { c } 3 = 0$ in terms of $\mathrm { a } , \mathrm { b }$.
(b) Let $\mathrm { a } , \mathrm { b } , \mathrm { c }$ be real numbers with $\mathrm { a } 2 + \mathrm { b } 2 + \mathrm { c } 2 = 1$. Show that the equation
$$\left| \begin{array} { c c c } a x - b y - c & b x + a y & c x + a \\ b x + a y & - a x + b y - c & c y + b \\ c x + a & c y + b & - a x - b y + c \end{array} \right| = 0 \text { represents a straight line. }$$
  1. (a) Let P be a point on the ellipse $\mathrm { x } 2 / \mathrm { a } 2 + \mathrm { y } 2 / \mathrm { b } 2 = 1,0 < \mathrm { b } < \mathrm { a }$. Let the line parallel to-qxis passing through P meet the circle $\mathrm { x } 2 + \mathrm { y } 2 = \mathrm { a } 2$ at the point Q such that P and Q are on the same side of - xxis . For two positive real numbers r and s , find the locus of the point R on PQ such that $\mathrm { PR } : \mathrm { RQ } = \mathrm { r } : \mathrm { s }$ as P varies over the ellipse.
    (b) If D is the area of a triangle with side lengths $\mathrm { a } , \mathrm { b } , \mathrm { c }$ then show that $\mathrm { D } < 1 / 4 \sqrt { } ( ( \mathrm { a } + \mathrm { b } + \mathrm { c } ) \mathrm { abc } )$.

Also show that the equality occurs in the above inequality if and only if $\mathrm { a } = \mathrm { b } = \mathrm { c }$.
Q13 Differential equations Applied Modeling with Differential Equations View
13. A hemispherical tank of radius 2 metres is initially full of water and has an outlet of 12 cm 2 cross sectional are at the bottom. The outlet is opened at some instant.
The flow through the outlet is according to the law $\mathrm { v } ( \mathrm { t } ) = 0.6 \sqrt { } ( 2 \mathrm { gh } ( \mathrm { t } ) )$, where $\mathrm { v } ( \mathrm { t } )$ and $\mathrm { h } ( \mathrm { t } )$ are respectively the velocity of the flow through the outlet and the height of water level above the outlet at time $t$, and $g$ is the acceleration due to gravity. Find the time it takes to empty the tank. (Hint : Form a differential equation by relating the decrease of water level to the outflow).
Q14 Probability Definitions Conditional Probability and Bayes' Theorem View
14. (a) An urn contains $m$ white and $n$ black balls. A ball is drawn at random and is put back into the urn along with k additional balls of the same colour as that of the ball drawn. A ball is again drawn at random. What is the probability that the ball drawn now is white?
(b) An unbiased die, with faces numbered $1,2,3,4,5,6$ is thrown n times and the list of n numbers showing up is noted. What is the probability that, among the numbers $1,2,3,4,5,6$ only three numbers appear in this list?
Q15 Vectors Introduction & 2D Dot Product Computation View
15. (a) Find 3 -dimensional vectors $\overrightarrow { v _ { 1 } } , \overrightarrow { v _ { 2 } } , \overrightarrow { v _ { 3 } }$ satisfying
$$\overrightarrow { v _ { 1 } } \cdot \overrightarrow { v _ { 1 } } = 4 , \overrightarrow { v _ { 1 } } \cdot \overrightarrow { v _ { 2 } } = - 2 , \overrightarrow { v _ { 1 } } \cdot \overrightarrow { v _ { 3 } } = 6 , \overrightarrow { v _ { 2 } } \cdot \overrightarrow { v _ { 2 } } = 2 , \overrightarrow { v _ { 2 } } \cdot \overrightarrow { v _ { 3 } } = - 5 , \overrightarrow { v _ { 3 } } \cdot \overrightarrow { v _ { 3 } } = 29 .$$
(b) Let $\vec { A } ( t ) = f _ { 1 } ( t ) \hat { i } + f _ { 2 } ( t ) \hat { j }$ and $B ( t ) = g _ { 1 } ( t ) \hat { i } + g _ { 2 } ( t ) \hat { j } , t \in [ 0,1 ]$, where $f _ { 1 \text {, } } \mathrm { f } _ { 2 } , \mathrm {~g} _ { 1 } , \mathrm {~g} _ { 2 }$ are continuous functions. If $\vec { A } ( \mathrm { t } )$ and $\vec { B } ( \mathrm { t } )$ are non-zero vectors for all t and $\vec { A } ( 0 ) = 2 \hat { \imath } + 3 \hat { \jmath } , \vec { A } ( 1 ) = 6 \hat { \imath } + 2 \hat { \jmath } , \vec { B } ( 0 ) = 3 \hat { \imath } + 2 \hat { \jmath }$ and $\vec { B } ( 1 ) = 2 \hat { \imath } + 6 \hat { j }$. The show that $\vec { A } ( t )$ and $\vec { B } ( t )$ are parallel for some $t$.