Common Patterns and Tips:
- For inverse trig functions, always check if the input is a standard value (like ½, √3/2, etc.)
- Remember that sin⁻¹ and tan⁻¹ are odd functions
- For inverse hyperbolic functions, use their logarithmic forms
- Pay attention to the range of each inverse function
Question 1: Evaluate Inverse Functions
Visualization of basic inverse trigonometric functions
Find the values of:
- \(\sin^{-1}(-\sqrt{3}/2)\)
- \(\tan^{-1}(1) - \tan^{-1}(-1)\)
- \(\cot^{-1}(1/\sqrt{3}) - \cot^{-1}(-1/\sqrt{3})\)
- \(\cosh^{-1}\sqrt{2}\)
- \(e^{[-\coth^{-1}(25/7)]}\)
- For \(\sin^{-1}(-\sqrt{3}/2)\):
- This is the angle whose sine is \(-\sqrt{3}/2\)
- We know that \(\sin(5\pi/6) = -\sqrt{3}/2\)
- Therefore, \(\sin^{-1}(-\sqrt{3}/2) = -\pi/3\)
- For \(\tan^{-1}(1) - \tan^{-1}(-1)\):
- \(\tan^{-1}(1) = \pi/4\)
- \(\tan^{-1}(-1) = -\pi/4\)
- Therefore, \(\tan^{-1}(1) - \tan^{-1}(-1) = \pi/2\)
- For \(\cot^{-1}(1/\sqrt{3}) - \cot^{-1}(-1/\sqrt{3})\):
- \(\cot^{-1}(1/\sqrt{3}) = \pi/6\)
- \(\cot^{-1}(-1/\sqrt{3}) = 5\pi/6\)
- Therefore, the difference is \(-\pi/3\)
- For \(\cosh^{-1}\sqrt{2}\):
- By definition, \(\cosh^{-1}x = \ln(x + \sqrt{x^2-1})\)
- Substituting \(x = \sqrt{2}\)
- Result is \(\ln(1 + \sqrt{2})\)
- For \(e^{[-\coth^{-1}(25/7)]}\):
- Recall that \(\coth^{-1}x = \frac{1}{2}\ln(\frac{x+1}{x-1})\)
- Substituting x = 25/7: \[\coth^{-1}(\frac{25}{7}) = \frac{1}{2}\ln(\frac{32/7}{18/7}) = \frac{1}{2}\ln(\frac{32}{18})\]
- Therefore: \[e^{[-\coth^{-1}(25/7)]} = e^{-\frac{1}{2}\ln(\frac{32}{18})} = (\frac{32}{18})^{-1/2} = \frac{3}{4}\]
Answers:
- a) \(-\pi/3\)
- b) \(\pi/2\)
- c) \(-\pi/3\)
- d) \(\ln(1 + \sqrt{2})\)
- e) \(\frac{3}{4}\)
Question 2: Special Identity
Prove that: \[\tan^{-1}x + \cot^{-1}x = \frac{\pi}{2}\] for all x
Visualization of the identity showing constant sum π/2
- Let's start by noting that \(\cot^{-1}x = \tan^{-1}(\frac{1}{x})\)
- Therefore, we need to prove: \[\tan^{-1}x + \tan^{-1}(\frac{1}{x}) = \frac{\pi}{2}\]
- Using the tangent addition formula: \[\tan(A + B) = \frac{\tan A + \tan B}{1 - \tan A \tan B}\]
- Let \(A = \tan^{-1}x\) and \(B = \tan^{-1}(\frac{1}{x})\)
- Then \(\tan(A + B) = \frac{x + \frac{1}{x}}{1 - x \cdot \frac{1}{x}} = \infty\)
- Therefore, \(A + B = \frac{\pi}{2}\)
The graph above visually confirms that this sum remains constant at π/2 for all valid x.
Question 3: Hyperbolic Function Identities
Derive the following identities:
Visualization of hyperbolic functions and their relationships
- Recall the definitions: \[\sinh x = \frac{e^x - e^{-x}}{2}\] \[\cosh x = \frac{e^x + e^{-x}}{2}\]
- For the first identity: \[\sinh(x \pm y) = \frac{e^{x\pm y} - e^{-(x\pm y)}}{2}\] \[= \frac{e^x e^{\pm y} - e^{-x} e^{\mp y}}{2}\]
- Expand this using the definitions above to get: \[\sinh x \cosh y \pm \cosh x \sinh y\]
- Similarly for the second identity, starting with: \[\cosh(x \pm y) = \frac{e^{x\pm y} + e^{-(x\pm y)}}{2}\]
- This expands to: \[\cosh x \cosh y \pm \sinh x \sinh y\]
The plot above shows how these functions behave and their relationships to each other.
Question 4: Triple Angle and Hyperbolic Formulas
Visualization of cos(3x) and its components
- For the triple angle formula: \[\cos(3x) = 4\cos^3(x) - 3\cos(x)\]
- Start with the double angle formula: \[\cos(2x) = 2\cos^2(x) - 1\]
- Then use the angle addition formula: \[\cos(3x) = \cos(2x + x)\]
- Substitute the double angle formula into this to get the triple angle formula
- For the hyperbolic formula: \[\cosh(2x) = 2\cosh^2(x) - 1\]
- Use the same process to derive the hyperbolic triple angle formula
Question 5: Inverse Hyperbolic Function Proofs
Visualization of inverse hyperbolic functions and their domains
- For the inverse hyperbolic functions: \[\text{arsinh}(x) = \ln(x + \sqrt{x^2 + 1})\] \[\text{arcosh}(x) = \ln(x + \sqrt{x^2 - 1})\] \[\text{artanh}(x) = \frac{1}{2}\ln(\frac{1+x}{1-x})\]
- These are derived by inverting the hyperbolic functions
- For the first identity: \[\text{arsinh}(x) = \ln(x + \sqrt{x^2 + 1})\]
- Start with \(y = \text{arsinh}(x)\) and use the definition of sinh
- Then solve for x to get the inverse function
Question 6: Domain Analysis
Visualization of functions with restricted domains
- For the domain-restricted functions: \[\ln(\sin x), \frac{1}{\sqrt{|\cos x|}}, \ln|\ln x|\]
- These functions have specific domains where they are defined
- For the first function: \[\ln(\sin x)\]
- Since the natural logarithm is only defined for positive values, the domain is: \[0 < \sin x \leq 1\]
- Similarly, analyze the other two functions to find their domains