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受欢迎的三角函数 >

cos^2(x)= 19/20

解答

cos^{2} (x) = \frac{19}{20}

解答

x = 0.22551 \dots + 2 πn, x = 2 π - 0.22551 \dots + 2 πn, x = 2.91607 \dots + 2 πn, x = - 2.91607 \dots + 2 πn

+1

度数

x = 12.92096 \dots^{\circ} + 36 0^{\circ} n, x = 347.07903 \dots^{\circ} + 36 0^{\circ} n, x = 167.07903 \dots^{\circ} + 36 0^{\circ} n, x = - 167.07903 \dots^{\circ} + 36 0^{\circ} n

求解步骤

cos^{2} (x) = \frac{19}{20}

用替代法求解

cos^{2} (x) = \frac{19}{20}

令

: cos (x) = u

u^{2} = \frac{19}{20}

u^{2} = \frac{19}{20} : u = \frac{95}{10}, u = - \frac{95}{10}

u^{2} = \frac{19}{20}

对于

x^{2} = f (a)

解为

x = f (a), - f (a)

u = \frac{19}{20}, u = - \frac{19}{20}

\frac{19}{20} = \frac{95}{10}

\frac{19}{20}

使用根式运算法则:

n \frac{a}{b} = \frac{n a}{n b},

假定

a \geq 0, b \geq 0

= \frac{19}{20}

20 = 25

20

20

质因数分解:

2^{2} \cdot 5

20

20

除以

220 = 10 \cdot 2

= 2 \cdot 10

10

除以

210 = 5 \cdot 2

= 2 \cdot 2 \cdot 5

2, 5

都是质数，因此无法进一步因数分解

= 2 \cdot 2 \cdot 5

= 2^{2} \cdot 5

= 2^{2} \cdot 5

使用根式运算法则:

n ab = n a n b

= 5 2^{2}

使用根式运算法则:

n a^{n} = a

2^{2} = 2

= 25

= \frac{19}{2 5}

\frac{19}{2 5}

有理化:

\frac{95}{10}

\frac{19}{2 5}

乘以共轭根式

\frac{5}{5}

= \frac{19 5}{2 5 5}

195 = 95

195

使用根式运算法则:

a b = a \cdot b

195 = 19 \cdot 5

= 19 \cdot 5

数字相乘:

19 \cdot 5 = 95

= 95

255 = 10

255

使用根式运算法则:

a a = a

55 = 5

= 2 \cdot 5

数字相乘:

2 \cdot 5 = 10

= 10

= \frac{95}{10}

= \frac{95}{10}

- \frac{19}{20} = - \frac{95}{10}

- \frac{19}{20}

化简

\frac{19}{20} : \frac{19}{2 5}

\frac{19}{20}

使用根式运算法则:

n \frac{a}{b} = \frac{n a}{n b},

假定

a \geq 0, b \geq 0

= \frac{19}{20}

20 = 25

20

20

质因数分解:

2^{2} \cdot 5

20

20

除以

220 = 10 \cdot 2

= 2 \cdot 10

10

除以

210 = 5 \cdot 2

= 2 \cdot 2 \cdot 5

2, 5

都是质数，因此无法进一步因数分解

= 2 \cdot 2 \cdot 5

= 2^{2} \cdot 5

= 2^{2} \cdot 5

使用根式运算法则:

n ab = n a n b

= 5 2^{2}

使用根式运算法则:

n a^{n} = a

2^{2} = 2

= 25

= \frac{19}{2 5}

= - \frac{19}{2 5}

- \frac{19}{2 5}

有理化:

- \frac{95}{10}

- \frac{19}{2 5}

乘以共轭根式

\frac{5}{5}

= - \frac{19 5}{2 5 5}

195 = 95

195

使用根式运算法则:

a b = a \cdot b

195 = 19 \cdot 5

= 19 \cdot 5

数字相乘:

19 \cdot 5 = 95

= 95

255 = 10

255

使用根式运算法则:

a a = a

55 = 5

= 2 \cdot 5

数字相乘:

2 \cdot 5 = 10

= 10

= - \frac{95}{10}

= - \frac{95}{10}

u = \frac{95}{10}, u = - \frac{95}{10}

u = cos (x)

代回

cos (x) = \frac{95}{10}, cos (x) = - \frac{95}{10}

cos (x) = \frac{95}{10}, cos (x) = - \frac{95}{10}

cos (x) = \frac{95}{10} : x = arccos (\frac{95}{10}) + 2 πn, x = 2 π - arccos (\frac{95}{10}) + 2 πn

cos (x) = \frac{95}{10}

使用反三角函数性质

cos (x) = \frac{95}{10}

cos (x) = \frac{95}{10}

的通解

cos (x) = a \Rightarrow x = arccos (a) + 2 πn, x = 2 π - arccos (a) + 2 πn

x = arccos (\frac{95}{10}) + 2 πn, x = 2 π - arccos (\frac{95}{10}) + 2 πn

x = arccos (\frac{95}{10}) + 2 πn, x = 2 π - arccos (\frac{95}{10}) + 2 πn

cos (x) = - \frac{95}{10} : x = arccos (- \frac{95}{10}) + 2 πn, x = - arccos (- \frac{95}{10}) + 2 πn

cos (x) = - \frac{95}{10}

使用反三角函数性质

cos (x) = - \frac{95}{10}

cos (x) = - \frac{95}{10}

的通解

cos (x) = - a \Rightarrow x = arccos (- a) + 2 πn, x = - arccos (- a) + 2 πn

x = arccos (- \frac{95}{10}) + 2 πn, x = - arccos (- \frac{95}{10}) + 2 πn

x = arccos (- \frac{95}{10}) + 2 πn, x = - arccos (- \frac{95}{10}) + 2 πn

合并所有解

x = arccos (\frac{95}{10}) + 2 πn, x = 2 π - arccos (\frac{95}{10}) + 2 πn, x = arccos (- \frac{95}{10}) + 2 πn, x = - arccos (- \frac{95}{10}) + 2 πn

以小数形式表示解

x = 0.22551 \dots + 2 πn, x = 2 π - 0.22551 \dots + 2 πn, x = 2.91607 \dots + 2 πn, x = - 2.91607 \dots + 2 πn

作图

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