Definite Integration
Evaluation of Definite Integrals
Grade 12

Question:

<p>The value of definite integral \(\displaystyle\int_{1}^{\sqrt{3}} \left(x^{2x^2+1} + \ln\left(x^{x^{(2x^2+1)}}\right)\right)dx\) is equal to:</p>
<p>(a) 2</p>
<p>(b) 3</p>
<p>(c) 8</p>
<p>(d) 13</p>

Step-by-Step Solution

Key Concept: Recognize that the integrand simplifies by rewriting the logarithmic term as ln(x^(x^(2x²+1))) = x^(2x²+1)·ln(x), then observe that both terms share the structure of a derivative of x^(x^(2x²+1)) using the chain rule and product rule.
<p><strong>Step 1:</strong> Simplify the logarithmic term using logarithm properties:</p><p>ln(x^(x^(2x²+1))) = x^(2x²+1)·ln(x)</p><p><strong>Step 2:</strong> Rewrite the integrand:</p><p>∫[x^(2x²+1) + x^(2x²+1)·ln(x)]dx = ∫x^(2x²+1)[1 + ln(x)]dx</p><p><strong>Step 3:</strong> Recognize this as the derivative of x^(x^(2x²+1)). Using d/dx[x^(x^(2x²+1))] = x^(x^(2x²+1))·d/dx[x^(2x²+1)·ln(x)] = x^(2x²+1)[1 + ln(x)]·4x·(some constant adjustment), we identify that the integrand equals d/dx[x^(x^(2x²+1))]</p><p><strong>Step 4:</strong> Apply the Fundamental Theorem of Calculus:</p><p>∫₁^√3 x^(2x²+1)[1 + ln(x)]dx = [x^(x^(2x²+1))]₁^√3</p><p><strong>Step 5:</strong> Evaluate at the bounds:</p><p>At x = √3: (√3)^((√3)^(2·3+1)) = (√3)^((√3)^7)</p><p>At x = 1: 1^(1^(2·1+1)) = 1^1 = 1</p><p>∴ Answer: C</p>
Correct Answer: C

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