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Functions of several variable

Total questions: 10

Worksheet time: 5mins

Name
Class
Date
1.

If x2+y2=25x^2+y^2=25 , then dydx=\frac{\text{d}y}{\text{d}x}=

a)

-x/y

b)

y/x

c)

-y/x

d)

x/y

2.

The Taylors expansion of first order of f(x)=excosyf\left(x\right)=e^x\cos y about (0,0) is

a)

1+x1+x

b)

1+xy1+x-y

c)

1+x(y22)1+x-\left(\frac{y^2}{2}\right)

d)

1+xysin(0)1+x-y\sin\left(0\right)

3.

For f(x,y)=x2y2f\left(x,y\right)=x^2-y^2 , the point (0,0) is

a)

Maximum

b)

Minimum

c)

Saddle point

d)

undeterminable

4.

Maximize f(x,y,z)=xyzf\left(x,y,z\right)=xyz subject to x+y+z=6x+y+z=6 . The maximum value occurs at

a)

(1,2,3)

b)

(2,2,2)

c)

(3,2,1)

d)

(0,3,3)

5.

If x=rcosϕ, y=rsinϕx=r\cos\phi,\ y=r\sin\phi , then J(x,yr,ϕ)J\left(\frac{x,y}{r,\phi}\right) is

a)

r2r^2

b)

0

c)

r

d)

-r

6.

If two functions are dependent, then their Jacobian is

a)

Positive

b)

Negative

c)

Zero

d)

Infinity

7.

The method of Lagrange multipliers is used to

a)

Approximate a function by series

b)

Find maxima/minima subject to a constraint

c)

Differentiate implicit functions

d)

Transform coordinates

8.

For a function f(x,y)f\left(x,y\right) , a point (x0,y0)\left(x_0,y_0\right) is called a critical point if

a)

f(x0,y0)=0f\left(x_0,y_0\right)=0

b)

f(x0,y0)f\left(x_0,y_0\right) is maximum only

c)

fx(x0,y0)=fy(x0,y0)=0f_x\left(x_0,y_0\right)=f_y\left(x_0,y_0\right)=0

d)

The point lies on the x- axis

9.

The Taylor series expansion of a function of two variables f(x,y)f\left(x,y\right) about (a,b)\left(a,b\right) is

a)

Expansion in powers of x and y only

b)

Expansion involving only linear terms

c)

A polynomial approximation without derivatives

d)

Expansion involving partial derivatives of ff at (a,b)\left(a,b\right)

10.

The Jacobian of the inverse transformation satisfies the property

a)

J(u,v x,y)×J(x,y u,v)=0J\left(\frac{u,v\ }{x,y}\right)\times J\left(\frac{x,y\ }{u,v}\right)=0

b)

J(u,v x,y)=J(x,y u,v)J\left(\frac{u,v\ }{x,y}\right)=J\left(\frac{x,y\ }{u,v}\right)

c)

J(u,v x,y)=0J\left(\frac{u,v\ }{x,y}\right)=0

d)

J(u,v x,y)×J(x,y u,v)=1J\left(\frac{u,v\ }{x,y}\right)\times J\left(\frac{x,y\ }{u,v}\right)=1