Math Problem Statement

MCT 311 PRACTICE QUESTIONS.docx

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solve number 2

Solution

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doc_text = '\n'.join([para.text for para in doc.paragraphs]) doc_textThe document contains a set of questions and mathematical problems related to vector calculus, electromagnetism, and other topics. From the text, the second problem appears to be:

"Determine the value of sin given that the angle between the following vectors is as follows:

  1. A = 2 - i; B = -3 + 5j - k
  2. C = 3i - j; D = 2i + 3j + k

where i, j, k are unit vectors."


To solve this, we can use the formula for the cosine of the angle between two vectors:

cosθ=ABAB\cos \theta = \frac{{\mathbf{A} \cdot \mathbf{B}}}{{|\mathbf{A}| |\mathbf{B}|}}

Then, since you are asked for sinθ\sin \theta, we use the identity:

sinθ=1cos2θ\sin \theta = \sqrt{1 - \cos^2 \theta}

Let’s calculate it step by step:

Step 1: Calculate the dot product AB\mathbf{A} \cdot \mathbf{B}

For vectors A and B: A=2i^j^,B=3i^+5j^k^A = 2\hat{i} - \hat{j}, \quad B = -3\hat{i} + 5\hat{j} - \hat{k} The dot product ABA \cdot B is: AB=(2)(3)+(1)(5)+(0)(1)=65=11A \cdot B = (2)(-3) + (-1)(5) + (0)(-1) = -6 - 5 = -11

Step 2: Find the magnitudes of A and B

The magnitude of vector AA: A=(2)2+(1)2=4+1=5|A| = \sqrt{(2)^2 + (-1)^2} = \sqrt{4 + 1} = \sqrt{5}

The magnitude of vector BB: B=(3)2+(5)2+(1)2=9+25+1=35|B| = \sqrt{(-3)^2 + (5)^2 + (-1)^2} = \sqrt{9 + 25 + 1} = \sqrt{35}

Step 3: Calculate cosθ\cos \theta

cosθ=115×35=11175\cos \theta = \frac{{-11}}{{\sqrt{5} \times \sqrt{35}}} = \frac{{-11}}{{\sqrt{175}}}

Step 4: Calculate sinθ\sin \theta

Now, using the identity for sinθ\sin \theta: sin2θ=1cos2θ=1(11175)2=1121175=54175\sin^2 \theta = 1 - \cos^2 \theta = 1 - \left(\frac{{-11}}{{\sqrt{175}}}\right)^2 = 1 - \frac{{121}}{{175}} = \frac{{54}}{{175}} sinθ=54175=54175=36175\sin \theta = \sqrt{\frac{{54}}{{175}}} = \frac{{\sqrt{54}}}{{\sqrt{175}}} = \frac{{3\sqrt{6}}}{{\sqrt{175}}}

Thus, the value of sinθ\sin \theta is approximately:

sinθ3×2.44913.2290.553\sin \theta \approx \frac{{3 \times 2.449}}{{13.229}} \approx 0.553


Would you like more detailed steps or further clarification on any part of this? Also, here are some related questions that could expand on this topic:

  1. What is the relationship between the dot product and the angle between vectors?
  2. How do you compute the angle between two vectors using the cross product?
  3. How can you use vector identities to simplify expressions in vector calculus?
  4. What is the significance of the sine and cosine functions in physics and engineering?
  5. How do you interpret the result of sinθ\sin \theta in practical applications like electromagnetism?

Tip: The magnitude of a vector is always positive, and the angle between vectors can range from 0 to 180 degrees, so be careful about the signs in your calculations!

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Math Problem Analysis

Mathematical Concepts

Vector Calculus
Dot Product
Trigonometry
Angle between Vectors

Formulas

cos(θ) = (A ⋅ B) / (|A| |B|)
sin(θ) = √(1 - cos²(θ))

Theorems

Dot Product Theorem
Vector Magnitude Theorem
Trigonometric Identity for sin(θ)

Suitable Grade Level

Grades 11-12