Chapter 2: Problem 202
Prove that: If \(\sin ^{-1} x+\sin ^{-1} y+\sin ^{-1} z=\frac{3 \pi}{2}\), then find the value of $$ x^{2012}+y^{2012}+z^{2012}-\frac{9}{x^{2013}+y^{2013}+z^{2013}} $$
Short Answer
Expert verified
The given equation simplifies to -6
Step by step solution
01
Interpret the given formula
The given formula is \(\sin ^{-1} x + \sin ^{-1} y + \sin ^{-1} z = \frac{3 \pi}{2}\). Since the sum of the angles in a triangle is equal to \(\pi\) and the sum here is exceeding \(\pi\), it implies that one of the angles is negative. So, we can assume \(\sin ^{-1} z = -\frac{\pi}{2}\), which means \(z = -1\). This makes \(\sin ^{-1} x + \sin ^{-1} y = \pi\). As the maximum value of \(\sin ^{-1} x\) is \(\frac{\pi}{2}\), this indicates that \(x = y = 1\). This assumption is made keeping in mind the range of inverse sin function which is between \(-\frac{\pi}{2}\) to \(\frac{\pi}{2}\).
02
Substitute the derived values
Now \(\sin ^{-1} z = -\frac{\pi}{2}\) implies \(z=-1\), and \(x = y = 1\). So, the expression \(x^{2012}+y^{2012}+z^{2012}-\frac{9}{x^{2013}+y^{2013}+z^{2013}}\) becomes \(1^{2012} + 1^{2012} + (-1)^{2012} - \frac{9}{1^{2013} + 1^{2013} + (-1)^{2013}}\)
03
Simplify the final equation
Now, simplifying the final part of the equation you get \(1 + 1 + 1 - \frac{9}{1 + 1 - 1} = 3 - 9\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Inverse Sine Function
The inverse sine function, often denoted as \( \sin^{-1} x \) or \( \arcsin(x) \), allows us to determine the angle whose sine is \( x \). This function is particularly useful in trigonometry when working backwards from the sine ratio to find an angle. It is important to remember the range of the inverse sine function:
- The range is \( -\frac{\pi}{2} \leq \sin^{-1} x \leq \frac{\pi}{2} \).
- This range corresponds to angles between \(-90^\circ\) and \(90^\circ\) on the unit circle.
Properties of Angles
Angles have well-defined properties that are pivotal when analyzing trigonometric functions and their inverses. Here are some essential properties to embrace:
- The sum of angles in a standard triangle is always \( \pi \) or \( 180^\circ \).
- An angle's measure can determine whether vectors or lines are considered perpendicular, parallel, or something else entirely.
- In a coordinate system, angles are vital in relating trigonometric values to geometric properties, such as direction or orientation.
Exponents in Algebraic Expressions
Exponents play a crucial role in algebra by simplifying expressions and solving equations. In the given problem, we use exponents to express power terms of \( x, y, \) and \( z \). Let's delve into some key concepts about exponents:
By simplifying, \( 1 + 1 + 1 \), and appropriately addressing any special behaviors in negative base exponents, we maintain clarity in the solution's verification, showing how exponent properties streamline problem-solving.
- An exponent indicates how many times a number, the base, is multiplied by itself.
- A positive integer exponent, such as \( 2012 \), makes calculations straightforward with known base numbers (e.g., \( 1^{2012} = 1 \), and \((-1)^{2012} = 1\)).
By simplifying, \( 1 + 1 + 1 \), and appropriately addressing any special behaviors in negative base exponents, we maintain clarity in the solution's verification, showing how exponent properties streamline problem-solving.