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로그의 성질과 방정식Log Properties & Equations · 문제집Worksheet

이름Name: ______________________   날짜Date: ______________________

문제Problem 1 몸풀기Warm-up

계산하여라.

(1)  log62+log63(2)  log212log23(1)\; \log_6 2 + \log_6 3 \qquad (2)\; \log_2 12 - \log_2 3

Evaluate:

(1)  log62+log63(2)  log212log23(1)\; \log_6 2 + \log_6 3 \qquad (2)\; \log_2 12 - \log_2 3

문제Problem 2 몸풀기Warm-up

log327\log_3 \sqrt{27}을 구하여라.

Evaluate log327\log_3 \sqrt{27}.

문제Problem 3 몸풀기Warm-up

log20.3010\log 2 \approx 0.3010, log30.4771\log 3 \approx 0.4771을 이용해 log12\log 12를 구하여라.

Using log20.3010\log 2 \approx 0.3010 and log30.4771\log 3 \approx 0.4771, find log12\log 12.

문제Problem 4 핵심Core

M=amM = a^m, N=anN = a^n으로 놓고 곱 법칙 logaMN=logaM+logaN\log_a MN = \log_a M + \log_a N과 거듭제곱 법칙 logaMk=klogaM\log_a M^k = k \log_a M을 증명하여라.

Setting M=amM = a^m, N=anN = a^n, prove the product law logaMN=logaM+logaN\log_a MN = \log_a M + \log_a N and the power law logaMk=klogaM\log_a M^k = k \log_a M.

문제Problem 5 핵심Core

log20.3010\log 2 \approx 0.3010, log30.4771\log 3 \approx 0.4771만으로 log5\log 5log15\log 15를 구하여라.

From log20.3010\log 2 \approx 0.3010 and log30.4771\log 3 \approx 0.4771 alone, find log5\log 5 and log15\log 15.

문제Problem 6 핵심Core

밑 변환 공식 logab=logcblogca\log_a b = \dfrac{\log_c b}{\log_c a}를 증명하고, 이로부터 역수 공식 logab=1logba\log_a b = \dfrac{1}{\log_b a}를 끌어내어라.

Prove the change-of-base formula logab=logcblogca\log_a b = \dfrac{\log_c b}{\log_c a}, and derive from it the reciprocal formula logab=1logba\log_a b = \dfrac{1}{\log_b a}.

문제Problem 7 핵심Core

log48\log_4 8log84\log_8 4를 구하고, 두 값의 곱을 확인하여라.

Find log48\log_4 8 and log84\log_8 4, and check their product.

문제Problem 8 핵심Core

log2x+log2(x2)=3\log_2 x + \log_2 (x - 2) = 3을 풀어라.

Solve log2x+log2(x2)=3\log_2 x + \log_2 (x - 2) = 3.

문제Problem 9 도전Challenge

log25=a\log_2 5 = a라 할 때, log450\log_4 50aa로 나타내어라.

Given log25=a\log_2 5 = a, express log450\log_4 50 in terms of aa.

문제Problem 10 도전Challenge

자연수 NN의 자릿수가 logN+1\lfloor \log N \rfloor + 1임을 밝히고, 이를 써서 21002^{100}의 자릿수를 구하여라. (log20.3010\log 2 \approx 0.3010)

Show that a natural number NN has logN+1\lfloor \log N \rfloor + 1 digits, and use this to count the digits of 21002^{100}. (log20.3010\log 2 \approx 0.3010)

문제Problem 11 도전Challenge

계산하여라:

1log2100+1log5100\frac{1}{\log_2 100} + \frac{1}{\log_5 100}

Evaluate:

1log2100+1log5100\frac{1}{\log_2 100} + \frac{1}{\log_5 100}

문제Problem 12 경시Contest

양수 xx

log2x+log4x+log8x=11\log_2 x + \log_4 x + \log_8 x = 11

을 만족할 때, xx를 구하여라.

A positive number xx satisfies

log2x+log4x+log8x=11.\log_2 x + \log_4 x + \log_8 x = 11.

Find xx.

문제Problem 13 경시Contest

log30.4771\log 3 \approx 0.4771을 이용해 31003^{100}의 자릿수와 첫째 자리 숫자를 구하여라. (log20.3010\log 2 \approx 0.3010)

Using log30.4771\log 3 \approx 0.4771, find the number of digits of 31003^{100} and its leading digit. (log20.3010\log 2 \approx 0.3010)