Textbook Question
Evaluate or simplify each expression without using a calculator. In e9x
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6. Exponential & Logarithmic Functions
Introduction to Logarithms
2:44 minutesProblem 99
Textbook Question
Given that log10 2 ≈ 0.3010 and log10 3 ≈ 0.4771, find each logarithm without using a calculator. log10 √30
Verified step by step guidance1
Recognize that the logarithm of a square root can be rewritten using the property \(\log_b \sqrt{x} = \log_b x^{1/2} = \frac{1}{2} \log_b x\).
Rewrite the given expression \(\log_{10} \sqrt{30}\) as \(\frac{1}{2} \log_{10} 30\).
Express 30 as a product of its prime factors: \(30 = 3 \times 10\) or more precisely \(30 = 3 \times 10 = 3 \times (2 \times 5)\), but since we only have logs for 2 and 3, use \(30 = 3 \times 10\) and then break down \(\log_{10} 30\) as \(\log_{10} (3 \times 10)\).
Use the logarithm product rule: \(\log_b (xy) = \log_b x + \log_b y\), so \(\log_{10} 30 = \log_{10} 3 + \log_{10} 10\).
Substitute the known values: \(\log_{10} 3 \approx 0.4771\) and \(\log_{10} 10 = 1\), then multiply the sum by \(\frac{1}{2}\) to find \(\log_{10} \sqrt{30}\).
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2mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Properties of Logarithms
Logarithms have specific properties that simplify calculations, such as the product rule (log_b(xy) = log_b(x) + log_b(y)) and the power rule (log_b(x^r) = r * log_b(x)). These allow breaking down complex expressions into simpler parts.
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Change of Base Property
Change of Base and Given Logarithm Values
Using given logarithm values like log_10(2) and log_10(3) helps compute other logarithms by expressing numbers in terms of these bases. This avoids calculator use by substituting known values into logarithmic expressions.
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Square Root as an Exponent
The square root of a number can be expressed as that number raised to the 1/2 power. This allows applying the power rule of logarithms, converting log(√x) into (1/2) * log(x), simplifying the calculation.
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