Chapter 14: Problem 10
Let \(F(x, y)=1+\sqrt{4-y^{2}}\) (a) Evaluate \(F(3,1) .\) (b) Find and sketch the domain of \(F\) (c) Find the range of \(F .\)
Short Answer
Expert verified
(a) 1+\sqrt{3}; (b) Domain: -2 \leq y \leq 2; (c) Range: [1, 3]
Step by step solution
01
Evaluate F(3, 1)
Substitute the values \(x = 3\) and \(y = 1\) into the function \(F(x, y) = 1 + \sqrt{4 - y^2}\). This gives \(F(3,1) = 1 + \sqrt{4 - 1^2}\). Simplify the expression to find \(F(3,1) = 1 + \sqrt{3}\).
02
Determine the Domain of F
The domain is determined based on the expression for \(F(x, y)\). The square root \(\sqrt{4 - y^2}\) is only defined for values where \(4 - y^2 \geq 0\), which simplifies to \(-2 \leq y \leq 2\). There are no restrictions on \(x\), so \(x\) can be any real number. Therefore, the domain is all \(x \in \mathbb{R}\) and \(-2 \leq y \leq 2\).
03
Sketch the Domain of F
In the xy-plane, the domain is represented by the strip defined by \(-2 \leq y \leq 2\) without any restrictions on \(x\). This corresponds to horizontal lines at \(y = -2\) and \(y = 2\), with all points \(x\) in between these two lines.
04
Find the Range of F
To determine the range, evaluate the possible values of \(F(x, y) = 1 + \sqrt{4 - y^2}\). Since \(-2 \leq y \leq 2\), \(\sqrt{4-y^2}\) ranges from \(0\) (when \(|y|=2\)) to \(2\) (when \(y=0\)). Thus, the function values \(F(x, y)\) range from \(1 + 0 = 1\) to \(1 + 2 = 3\). Therefore, the range is \([1, 3]\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Domain and Range of Functions
Understanding the domain and range of a function is crucial in multivariable calculus. These concepts help us identify where a function is defined and the possible output values.
To find the domain of a function like \(F(x, y) = 1 + \sqrt{4 - y^2}\), consider the conditions under which the function makes sense. In this case, we look at the expression inside the square root: \(4 - y^2\). The square root is only defined for non-negative inputs, which means \(4 - y^2\geq 0\). Solving this inequality gives us \(-2 \leq y \leq 2\). There are no restrictions on \(x\), so it can be any real number.
To find the domain of a function like \(F(x, y) = 1 + \sqrt{4 - y^2}\), consider the conditions under which the function makes sense. In this case, we look at the expression inside the square root: \(4 - y^2\). The square root is only defined for non-negative inputs, which means \(4 - y^2\geq 0\). Solving this inequality gives us \(-2 \leq y \leq 2\). There are no restrictions on \(x\), so it can be any real number.
- Domain: All \(x \in \mathbb{R}\) and \(-2 \leq y \leq 2\).
- Range Determination: With the determined domain, you can find the range by evaluating the function's possible output values. For our function, as \(y\) changes from \(-2\) to \(2\), the expression \(\sqrt{4 - y^2}\) ranges from \(0\) to \(2\).
- Range: The range of \(F(x, y)\) is \([1, 3]\), calculated from \(1 + 0\) to \(1 + 2\).
Evaluating Functions
When given a function and a set of variables to evaluate, it's a matter of plugging in these variables into the function's formula. Take the function \(F(x, y) = 1 + \sqrt{4 - y^2}\) and say we are given \(x = 3\) and \(y = 1\).
To evaluate this function at \(F(3, 1)\), substitute \(x = 3\) and \(y = 1\) into the function. So it becomes:
To evaluate this function at \(F(3, 1)\), substitute \(x = 3\) and \(y = 1\) into the function. So it becomes:
- \(F(3, 1) = 1 + \sqrt{4 - 1^2}\)
- Calculate \(\sqrt{4 - 1^2} = \sqrt{4 - 1} = \sqrt{3}\)
- Therefore, \(F(3, 1) = 1 + \sqrt{3}\)
Square Root Function
The square root function is a fundamental mathematical function that often appears in different contexts, from simple algebra to complex multivariable calculus problems.
For the function \(F(x, y) = 1 + \sqrt{4 - y^2}\), the square root component \(\sqrt{4 - y^2}\) dictates essential aspects of the function’s behavior. The square root function has certain key properties:
For the function \(F(x, y) = 1 + \sqrt{4 - y^2}\), the square root component \(\sqrt{4 - y^2}\) dictates essential aspects of the function’s behavior. The square root function has certain key properties:
- Non-negativity: The expression inside the square root (the radicand) must be zero or positive because you cannot take the square root of a negative number in the real number system.
- Continuity and Smoothness: The function is continuous and smooth over its domain, except possibly at boundary points, such as where \(y = \pm 2\).
- Effect on Range: As seen in our function, the range is partly determined by how the square root behaves, going from its minimum value (here, 0) to its maximum value (here, 2).