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Using only principal values of inverse functions, describe the set $A=\left\{x\geq0:\tan^{-1}(2x)+\tan^{-1}(3x)=\dfrac{\pi}{4}\right\}$.
Apply the addition formula: $\tan^{-1}(2x)+\tan^{-1}(3x)=\tan^{-1}\!\left(\dfrac{5x}{1-6x^2}\right)$ when $6x^2<1$.
Setting equal to $\pi/4$: $\dfrac{5x}{1-6x^2}=1 \Rightarrow 5x=1-6x^2 \Rightarrow 6x^2+5x-1=0$
$x=\dfrac{-5\pm\sqrt{25+24}}{12}=\dfrac{-5\pm7}{12}$
$x=\dfrac{2}{12}=\dfrac{1}{6}$ or $x=\dfrac{-12}{12}=-1$.
Since $x\geq0$, only $x=\dfrac{1}{6}$ is valid. Check: $6\cdot(1/6)^2=1/6<1$ ✓. So $A=\{1/6\}$ — a singleton.
A software firm plans to migrate its infrastructure to a new VPS. The project requires an initial outlay of $10,000 and is expected to generate net cash flows of $4,000, $5,000, and $6,000 over three years. If the cost of capital is 10%, what is the Net Present Value (NPV)?
Using the formula $NPV = -I_0 + \sum \frac{CF_t}{(1+i)^t}$, we get: $-10,000 + 3,636 + 4,132 + 4,508 = 2,276$. (Calculated precisely: $NPV = 2104$).
- $Na^{+}$ from $NaCl$ and $Na_{2}SO_{4}$ (+1)
- $Ba^{2+}$ from $BaCl_{2}$ (+2)
- $Al^{3+}$ from $AlCl_{3}$ (+3)
The acidity of the female urethra is neutralized by secretions from which male gland?
Prostate gland secretes a slightly alkaline fluid (pH ~7.5) that neutralizes acidic vaginal pH and urethral acidity, protecting sperm. Cowper's gland secretes pre-ejaculate; seminal vesicle provides fructose.
Therefore \(X = 1.3 - 0.1 = 1.20\).
Sickle Cell Disease — Types of Crisis:
| Crisis | Features | Management |
|---|---|---|
| Vaso-occlusive (Painful) | Most common; bone/joint pain, dactylitis (hand-foot syndrome in young children), fever | IV fluids, analgesia (NSAIDs → opioids), O₂ |
| Aplastic Crisis | Parvovirus B19 infects erythroid precursors; reticulocytopenia; severe anemia; spleen not enlarged | Urgent blood transfusion |
| Splenic Sequestration | Blood pools in spleen; massive splenomegaly; hypovolemic shock; age <5 yrs | IV fluids, blood transfusion, splenectomy |
| Hemolytic Crisis | Accelerated hemolysis; jaundice; often with G6PD deficiency | Identify trigger, transfuse if severe |
Key clue: Parvovirus B19 temporarily shuts down erythropoiesis → reticulocytes drop to near zero → Hb falls dramatically. The spleen is already infarcted by age 5 (autosplenectomy) in sickle cell, so not palpable.
Priority nursing action: Arrange urgent blood transfusion, monitor Hb, SpO₂, vital signs closely.
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