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VTU First Year Engineering (C Cycle) (Semester 1)
Engineering Maths 1
December 2014
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

1 (a) If Y=cos(m log x), prove that $x^2 y_{n+2}+ (2n+1)xy_{n+1} + (m^2 + n^2)y_s=0$
7 M
1 (b) Find the angle intersection between the curves $r=a \log \theta \ and \ r = \dfrac {n}{\log \theta}$
6 M
1 (c) Derive an expression to find radius of curvature in Cartesian form.
7 M

2 (a) $If \ \sin^{-1} y=2 \log (x+1) \ prove \ that \ (x^2 +1) y_{n+2} + (2n+1) (x+1)y_{n+1}+ (n^2 + 4)y_n=0$
7 M
2 (b) Find the pedal equation rn=sec hn?
6 M
2 (c) Show that the radius of curvature of the curve $x^3 + y^3 = 3xy \ at \ \left ( \dfrac {3}{2}, \dfrac {3}{2} \right ) \ is \ \dfrac {-3}{8\sqrt{2}}$
7 M

3 (a) Find the first four non zero terms in the expansion of $f(x) = \dfrac {x}{e^{x-1}}$
7 M
3 (b) $If \ \cos u = \dfrac {x+y}{\sqrt{x}+ \sqrt{y}} \ show \ that \ x\dfrac {\partial u}{\partial x} + y \dfrac {\partial u}{\partial y} = - \dfrac {\cot u}{2}$
6 M
3 (c) $Find \ \dfrac {\partial (u,v,w)}{\partial (x,yz)} \ where \ u=x^2+y^2+z^2, \ v=xy+yz + zx \ and \ w=x+y+z$ Hence interpret the result.
7 M

4 (a) If w=f(x,y), x=r cos &theta, y=r sin ? show that $\left ( \dfrac {\partial t}{\partial x} \right )^2 + \left ( \dfrac {\partial t}{\partial y} \right )^2 - \left ( \dfrac {\partial w}{\partial r} \right )^2 = \dfrac {1}{r^2} \left ( \dfrac {\partial w}{\partial \theta} \right )^2$
7 M
4 (b) Evaluate $\lim_{x\to 0} \left ( \dfrac {\sin x} {x}\right )^{\frac {1}{x}}$
6 M
4 (c) Examine the function f(x,y)=1+sin(x2+y2) for extremum.
7 M

5 (a) A particle moves along the curve x=2t2, y=t2-4t, z=3t-5. Find the components of velocity and acceleration at t=1 in the direction $\widehat{i}-2\widehat{j}+2\widehat{k}$
7 M
5 (b) Using differentiation under integral sign, evaluate $\int^\infty_0 \dfrac{e^{-\alpha x}\sin x}{x}dx$
7 M
5 (c) Use general rules to trace the curve y2(a-x)=x3, a>0
6 M

6 (a) $If \ \overrightarrow{r} = x\widehat{i} + y\widehat{j}+ z\widehat{k} \ and \ |\overrightarrow{r}|= r. \ Find \ grad \ div \left ( \dfrac {\overrightarrow{r}}{r} \right )$
7 M

7 (a) Obtain the reduction formula for $\int^{\frac {\pi}{2}}_0 \cos^n xdx$
7 M
7 (b) Solve (xy3+y)dx+2(x2y2+x+y4)dy=0
6 M
7 (c) Show that the orthogonal trajectories of the family of cardioids $r= a \cos^2 \left ( \dfrac {\theta}{2} \right )$ is another family of cardioids $r= b \sin^2 \left ( \dfrac {\theta}{2} \right )$
7 M

8 (a) $Evaluate \ \int^\pi_0 x \sin^2 x \cos^4 xdx$
7 M
8 (b) $Solve \ \dfrac {dy}{dx}- y \tan x=y^2 \sec x$
6 M
8 (c) If the temperature of the air is 30°C and the substance cools from 100°C to 70°C in 15 minutes, find when the temperature will be 40°C.
7 M

9 (a) Solve 3x-y+2z=12, x+2y+3z=11, 2x-2y-z=2 by Gauss elimination method.
6 M
9 (b) Diagonalize the matrix $A= \begin{bmatrix}-1 &1 &2 \\0 &-2 &-1 \\0 &0 &-3 \end{bmatrix}$
7 M
9 (c) Determine the largest eigen value and the corresponding eigen vector of $A= \begin{bmatrix}1 &3 &-1 \\3 &2 &4 \\-1 &4 &10 \end{bmatrix}$ Staring with [0, 0, 1]? as the initial eigenvector. Perform 5 iterations.
7 M

10 (a) Show that the transformation $y_1 = x_1 + 2x_2 +5x_3 , \ y_2 = 2x_3 + 4x_2 + 11 x_3 , \ y_3 = -x_2 + 2x_3$ is regular and find the inverse transformation.
6 M
10 (b) Solve by LU decomposition method 2x+y+4z=12, 8x-3y+2z=20, 4x+11y-z=33
7 M
10 (c) Reduce the quadratic form 2x2+2y2-2xy-2yz-2zx into canonical form. Hence indicate its nature, rank, index and signature.
7 M

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