Question

I) Find the directional derivative of 𝑓(π‘₯, 𝑦) = π‘₯ sin 𝑦 at (1,0) in the direction of the unit vector that make an angle of πœ‹/4 with positive π‘₯-axis.

190

likes
949 views

Answer to a math question I) Find the directional derivative of 𝑓(π‘₯, 𝑦) = π‘₯ sin 𝑦 at (1,0) in the direction of the unit vector that make an angle of πœ‹/4 with positive π‘₯-axis.

Expert avatar
Bud
4.6
96 Answers
To find the directional derivative of a function, we need to calculate the dot product of the gradient vector of the function and the unit vector in the given direction.

The gradient vector of the function f(x, y) is given by the partial derivatives of f with respect to each variable.

Let's find the partial derivatives of f(x, y):

\frac{\partial f}{\partial x} = \frac{\partial}{\partial x} (x \sin y) = \sin y

\frac{\partial f}{\partial y} = \frac{\partial}{\partial y} (x \sin y) = x \cos y

Now, we can find the gradient vector:

\nabla f = \left(\frac{\partial f}{\partial x}, \frac{\partial f}{\partial y}\right) = \left(\sin y, x \cos y\right)

The unit vector that makes an angle of πœ‹/4 with the positive π‘₯-axis is:

\mathbf{u}=\left(\cos\frac{\pi}{4},\sin\frac{\pi}{4}\right)=\left(\frac{\sqrt{2}}{2},\frac{\sqrt{2}}{2}\right)

Now, we can calculate the dot product of the gradient vector and the unit vector:

\nabla f\cdot\mathbf{u}=\left(\sin y,x\cos y\right)\cdot\left(\frac{\sqrt{2}}{2},\frac{\sqrt{2}}{2}\right)=\frac{\sqrt{2}}{2}\sin y+\frac{\sqrt{2}}{2}x\cos y

Substituting the coordinates of the point (1, 0) into the equation above:

\nabla f\cdot\mathbf{u}=\frac{\sqrt{2}}{2}\cdot\sin0+\frac{\sqrt{2}}{2}\cdot1\cdot\cos0=\frac{\sqrt{2}}{2}\cdot0+\frac{\sqrt{2}}{2}\cdot1\cdot1=\frac{\sqrt{2}}{2}

Answer: The directional derivative of f(x, y) = x sin y at (1, 0) in the direction of the unit vector that makes an angle of πœ‹/4 with the positive π‘₯-axis is \frac{\sqrt{2}}{2} .

Frequently asked questions (FAQs)
Math question: Graph the inequality 3x + 2y ≀ 10. Plot the solution on a coordinate plane.
+
Question: Simplify √(3) + √(27) - √(12)
+
What is the vertex form of a parabola with a vertex at (2, -3)?
+
New questions in Mathematics
The patient is prescribed a course of 30 tablets. The tablets are prescribed β€œ1 tablet twice a day”. How many days does a course of medication last?
A college believes that 22% of applicants to that school have parents who have remarried. How large a sample is needed to estimate the true proportion of students who have parents who have remarried to within 5 percentage points?
Jose bought 3/4 of oil and his sister bought 6/8, which of the two bought more oil?
A drawer contains three pairs of white socks, five pairs of black socks and two pairs of red socks. Caden randomly selects two pairs of socks on his way to the gym. What is the probability that both pairs of socks are black?
4x567
Suppose 56% of politicians are lawyers if a random sample of size 564 is selected, what is the probability that the proportion of politicians who are lawyers will differ from the total politicians proportions buy more than 4% round your answer to four decimal places
Equivalent expression of the sequence (3n-4)-(n-2)
The beta of a company is 1.51 while its financial leverage is 27%. What is then its unlevered beta if the corporate tax rate is 40%? (4 decimal places)
7/6-(-1/9)
How many anagrams of the word STROMEC there that do not contain STROM, MOST, MOC or CEST as a subword? By subword is meant anything that is created by omitting some letters - for example, the word EMROSCT contains both MOC and MOST as subwords.
Suppose that you use 4.29 g of Iron in the chemical reaction: 2Fe(s) + 3 Cu2 + (aq) 2Fe 3 + (aq) + 3Cu(s ) - . What is the theoretical yield of Cu (s), in grams?
Show this compound proposition to be true or false. Paris is the capital of England or Rome is the capital of Italy
The points (-5,-4) and (3,6) are the ends of the diameter of the circle calculate subequation
Jasminder has made 55% of the recipes in a particular cookbook. If there are 9 recipes that he has never made, how many recipes does the cookbook contain?
For what values of m is point P (m, 1 - 2m) in the 2⁰ quadrant?
Your grandfather has run a small high street pharmacy for 40 years. After much persuasion, he has agreed to open a digital store online. List 5 potential ways to improve sales and/or margins by having a digital pharmacy through the utilisation of historic or new sales data.
A block slides across the floor with a force of 20N, which has an angle of 30Β°. The mass of the block is 2kg and the coefficient of friction is 0.1. Calculate the value of all the forces involved in this system and finally the value of the acceleration.
To paint a 250 m wall, a number of workers were employed. If the wall were 30 m longer, 9 more workers would be needed. How many were employed at the beginning?
Today a father deposits $12,500 in a bank that pays 8% annual interest. Additionally, make annual contributions due of $2,000 annually for 3 years. The fund is for your son to receive an annuity and pay for his studies for 5 years. If the child starts college after 4 years, how much is the value of the annuity? solve how well it is for an exam
-1/3x+15=18