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受欢迎的三角函数 >

(-1/5)*cos(2 pi/5 (x+1))+1>= 16/15

解答

(- \frac{1}{5}) \cdot cos (2 \frac{π}{5} (x + 1)) + 1 \geq \frac{16}{15}

解答

\frac{5 arccos ( - \frac{1}{3} ) - 2 π}{2 π} + 5 n \leq x \leq \frac{8 π - 5 arccos ( - \frac{1}{3} )}{2 π} + 5 n

+2

间隔符号

[\frac{5 arccos ( - \frac{1}{3} ) - 2 π}{2 π} + 5 n, \frac{8 π - 5 arccos ( - \frac{1}{3} )}{2 π} + 5 n]

十进制

0.52043 \dots + 5 n \leq x \leq 2.47956 \dots + 5 n

求解步骤

(- \frac{1}{5}) cos (2 \cdot \frac{π}{5} (x + 1)) + 1 \geq \frac{16}{15}

将

1

到右边

(- \frac{1}{5}) cos (2 \frac{π}{5} (x + 1)) + 1 \geq \frac{16}{15}

两边减去

1

(- \frac{1}{5}) cos (2 \frac{π}{5} (x + 1)) + 1 - 1 \geq \frac{16}{15} - 1

化简

(- \frac{1}{5}) cos (2 \frac{π}{5} (x + 1)) + 1 - 1 \geq \frac{16}{15} - 1

化简

(- \frac{1}{5}) cos (2 \frac{π}{5} (x + 1)) + 1 - 1 : (- \frac{1}{5}) cos (2 \frac{π}{5} (x + 1))

(- \frac{1}{5}) cos (2 \frac{π}{5} (x + 1)) + 1 - 1

同类项相加:

1 - 1 \geq 0

= (- \frac{1}{5}) cos (2 \frac{π}{5} (x + 1))

化简

\frac{16}{15} - 1 : \frac{1}{15}

\frac{16}{15} - 1

将项转换为分式:

1 = \frac{1 \cdot 15}{15}

= - \frac{1 \cdot 15}{15} + \frac{16}{15}

因为分母相等，所以合并分式:

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{- 1 \cdot 15 + 16}{15}

- 1 \cdot 15 + 16 = 1

- 1 \cdot 15 + 16

数字相乘:

1 \cdot 15 = 15

= - 15 + 16

数字相加/相减:

- 15 + 16 = 1

= 1

= \frac{1}{15}

(- \frac{1}{5}) cos (2 \frac{π}{5} (x + 1)) \geq \frac{1}{15}

(- \frac{1}{5}) cos (2 \frac{π}{5} (x + 1)) \geq \frac{1}{15}

(- \frac{1}{5}) cos (2 \frac{π}{5} (x + 1)) \geq \frac{1}{15}

在两边乘以

- 1

(- \frac{1}{5}) cos (2 \frac{π}{5} (x + 1)) \geq \frac{1}{15}

两边乘以 -1（不等式变号）

(- \frac{1}{5}) cos (2 \frac{π}{5} (x + 1)) (- 1) \leq \frac{1 \cdot ( - 1 )}{15}

化简

\frac{1}{5} cos (2 \frac{π}{5} (x + 1)) \leq - \frac{1}{15}

\frac{1}{5} cos (2 \frac{π}{5} (x + 1)) \leq - \frac{1}{15}

在两边乘以

5

\frac{1}{5} cos (2 \frac{π}{5} (x + 1)) \leq - \frac{1}{15}

在两边乘以

5

5 \cdot \frac{1}{5} cos (2 \frac{π}{5} (x + 1)) \leq 5 (- \frac{1}{15})

化简

5 \cdot \frac{1}{5} cos (2 \frac{π}{5} (x + 1)) \leq 5 (- \frac{1}{15})

化简

5 \cdot \frac{1}{5} cos (2 \frac{π}{5} (x + 1)) : cos (2 \frac{π}{5} (x + 1))

5 \cdot \frac{1}{5} cos (2 \frac{π}{5} (x + 1))

分式相乘:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{1 \cdot 5}{5} cos (2 \frac{π}{5} (x + 1))

约分:

5

= cos (2 \frac{π}{5} (x + 1)) \cdot 1

乘以:

cos (2 \frac{π}{5} (x + 1)) \cdot 1 = cos (2 \frac{π}{5} (x + 1))

= cos (2 \frac{π}{5} (x + 1))

化简

5 (- \frac{1}{15}) : - \frac{1}{3}

5 (- \frac{1}{15})

去除括号:

(- a) = - a

= - 5 \cdot \frac{1}{15}

分式相乘:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= - \frac{1 \cdot 5}{15}

数字相乘:

1 \cdot 5 = 5

= - \frac{5}{15}

约分:

5

= - \frac{1}{3}

cos (2 \frac{π}{5} (x + 1)) \leq - \frac{1}{3}

cos (2 \frac{π}{5} (x + 1)) \leq - \frac{1}{3}

cos (2 \frac{π}{5} (x + 1)) \leq - \frac{1}{3}

对于

cos (x) \leq a

，若

- 1 < a < 1

，则

arccos (a) + 2 πn \leq x \leq 2 π - arccos (a) + 2 πn

arccos (- \frac{1}{3}) + 2 πn \leq 2 \cdot \frac{π}{5} (x + 1) \leq 2 π - arccos (- \frac{1}{3}) + 2 πn

若

a \leq u \leq b

，则

a \leq u and u \leq b

arccos (- \frac{1}{3}) + 2 πn \leq 2 \cdot \frac{π}{5} (x + 1) and 2 \cdot \frac{π}{5} (x + 1) \leq 2 π - arccos (- \frac{1}{3}) + 2 πn

arccos (- \frac{1}{3}) + 2 πn \leq 2 \cdot \frac{π}{5} (x + 1) : x \geq \frac{5 arccos ( - \frac{1}{3} ) - 2 π}{2 π} + 5 n

arccos (- \frac{1}{3}) + 2 πn \leq 2 \cdot \frac{π}{5} (x + 1)

交换两边

2 \cdot \frac{π}{5} (x + 1) \geq arccos (- \frac{1}{3}) + 2 πn

化简

2 \cdot \frac{π}{5} : \frac{2 π}{5}

2 \cdot \frac{π}{5}

分式相乘:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{π 2}{5}

\frac{2 π}{5} (x + 1) \geq arccos (- \frac{1}{3}) + 2 πn

在两边乘以

5

\frac{2 π}{5} (x + 1) \geq arccos (- \frac{1}{3}) + 2 πn

在两边乘以

5

5 \cdot \frac{2 π}{5} (x + 1) \geq 5 arccos (- \frac{1}{3}) + 5 \cdot 2 πn

化简

5 \cdot \frac{2 π}{5} (x + 1) \geq 5 arccos (- \frac{1}{3}) + 5 \cdot 2 πn

化简

5 \cdot \frac{2 π}{5} (x + 1) : 2 π (x + 1)

5 \cdot \frac{2 π}{5} (x + 1)

分式相乘:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{2 \cdot 5 π}{5} (x + 1)

约分:

5

= (x + 1) \cdot 2 π

化简

5 arccos (- \frac{1}{3}) + 5 \cdot 2 πn : 5 arccos (- \frac{1}{3}) + 10 πn

5 arccos (- \frac{1}{3}) + 5 \cdot 2 πn

数字相乘:

5 \cdot 2 = 10

= 5 arccos (- \frac{1}{3}) + 10 πn

2 π (x + 1) \geq 5 arccos (- \frac{1}{3}) + 10 πn

2 π (x + 1) \geq 5 arccos (- \frac{1}{3}) + 10 πn

2 π (x + 1) \geq 5 arccos (- \frac{1}{3}) + 10 πn

两边除以

2 π

2 π (x + 1) \geq 5 arccos (- \frac{1}{3}) + 10 πn

两边除以

2 π

\frac{2 π ( x + 1 )}{2 π} \geq \frac{5 arccos ( - \frac{1}{3} )}{2 π} + \frac{10 πn}{2 π}

化简

\frac{2 π ( x + 1 )}{2 π} \geq \frac{5 arccos ( - \frac{1}{3} )}{2 π} + \frac{10 πn}{2 π}

化简

\frac{2 π ( x + 1 )}{2 π} : x + 1

\frac{2 π ( x + 1 )}{2 π}

数字相除:

\frac{2}{2} = 1

= \frac{π ( x + 1 )}{π}

约分:

π

= x + 1

化简

\frac{5 arccos ( - \frac{1}{3} )}{2 π} + \frac{10 πn}{2 π} : \frac{5 arccos ( - \frac{1}{3} )}{2 π} + 5 n

\frac{5 arccos ( - \frac{1}{3} )}{2 π} + \frac{10 πn}{2 π}

消掉

\frac{10 πn}{2 π} : 5 n

\frac{10 πn}{2 π}

消掉

\frac{10 πn}{2 π} : 5 n

\frac{10 πn}{2 π}

数字相除:

\frac{10}{2} = 5

= \frac{5 πn}{π}

约分:

π

= 5 n

= 5 n

= \frac{5 arccos ( - \frac{1}{3} )}{2 π} + 5 n

x + 1 \geq \frac{5 arccos ( - \frac{1}{3} )}{2 π} + 5 n

x + 1 \geq \frac{5 arccos ( - \frac{1}{3} )}{2 π} + 5 n

x + 1 \geq \frac{5 arccos ( - \frac{1}{3} )}{2 π} + 5 n

将

1

到右边

x + 1 \geq \frac{5 arccos ( - \frac{1}{3} )}{2 π} + 5 n

两边减去

1

x + 1 - 1 \geq \frac{5 arccos ( - \frac{1}{3} )}{2 π} + 5 n - 1

化简

x \geq \frac{5 arccos ( - \frac{1}{3} )}{2 π} + 5 n - 1

x \geq \frac{5 arccos ( - \frac{1}{3} )}{2 π} + 5 n - 1

化简

\frac{5 arccos ( - \frac{1}{3} )}{2 π} - 1 : \frac{5 arccos ( - \frac{1}{3} ) - 2 π}{2 π}

\frac{5 arccos ( - \frac{1}{3} )}{2 π} - 1

将项转换为分式:

1 = \frac{1 \cdot 2 π}{2 π}

= \frac{5 arccos ( - \frac{1}{3} )}{2 π} - \frac{1 \cdot 2 π}{2 π}

因为分母相等，所以合并分式:

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{5 arccos ( - \frac{1}{3} ) - 1 \cdot 2 π}{2 π}

数字相乘:

1 \cdot 2 = 2

= \frac{5 arccos ( - \frac{1}{3} ) - 2 π}{2 π}

x \geq \frac{5 arccos ( - \frac{1}{3} ) - 2 π}{2 π} + 5 n

2 \cdot \frac{π}{5} (x + 1) \leq 2 π - arccos (- \frac{1}{3}) + 2 πn : x \leq \frac{8 π - 5 arccos ( - \frac{1}{3} )}{2 π} + 5 n

2 \cdot \frac{π}{5} (x + 1) \leq 2 π - arccos (- \frac{1}{3}) + 2 πn

化简

2 \cdot \frac{π}{5} : \frac{2 π}{5}

2 \cdot \frac{π}{5}

分式相乘:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{π 2}{5}

\frac{2 π}{5} (x + 1) \leq 2 π - arccos (- \frac{1}{3}) + 2 πn

在两边乘以

5

\frac{2 π}{5} (x + 1) \leq 2 π - arccos (- \frac{1}{3}) + 2 πn

在两边乘以

5

5 \cdot \frac{2 π}{5} (x + 1) \leq 5 \cdot 2 π - 5 arccos (- \frac{1}{3}) + 5 \cdot 2 πn

化简

5 \cdot \frac{2 π}{5} (x + 1) \leq 5 \cdot 2 π - 5 arccos (- \frac{1}{3}) + 5 \cdot 2 πn

化简

5 \cdot \frac{2 π}{5} (x + 1) : 2 π (x + 1)

5 \cdot \frac{2 π}{5} (x + 1)

分式相乘:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{2 \cdot 5 π}{5} (x + 1)

约分:

5

= (x + 1) \cdot 2 π

化简

5 \cdot 2 π - 5 arccos (- \frac{1}{3}) + 5 \cdot 2 πn : 10 π - 5 arccos (- \frac{1}{3}) + 10 πn

5 \cdot 2 π - 5 arccos (- \frac{1}{3}) + 5 \cdot 2 πn

数字相乘:

5 \cdot 2 = 10

= 10 π - 5 arccos (- \frac{1}{3}) + 10 πn

2 π (x + 1) \leq 10 π - 5 arccos (- \frac{1}{3}) + 10 πn

2 π (x + 1) \leq 10 π - 5 arccos (- \frac{1}{3}) + 10 πn

2 π (x + 1) \leq 10 π - 5 arccos (- \frac{1}{3}) + 10 πn

两边除以

2 π

2 π (x + 1) \leq 10 π - 5 arccos (- \frac{1}{3}) + 10 πn

两边除以

2 π

\frac{2 π ( x + 1 )}{2 π} \leq \frac{10 π}{2 π} - \frac{5 arccos ( - \frac{1}{3} )}{2 π} + \frac{10 πn}{2 π}

化简

\frac{2 π ( x + 1 )}{2 π} \leq \frac{10 π}{2 π} - \frac{5 arccos ( - \frac{1}{3} )}{2 π} + \frac{10 πn}{2 π}

化简

\frac{2 π ( x + 1 )}{2 π} : x + 1

\frac{2 π ( x + 1 )}{2 π}

数字相除:

\frac{2}{2} = 1

= \frac{π ( x + 1 )}{π}

约分:

π

= x + 1

化简

\frac{10 π}{2 π} - \frac{5 arccos ( - \frac{1}{3} )}{2 π} + \frac{10 πn}{2 π} : 5 - \frac{5 arccos ( - \frac{1}{3} )}{2 π} + 5 n

\frac{10 π}{2 π} - \frac{5 arccos ( - \frac{1}{3} )}{2 π} + \frac{10 πn}{2 π}

消掉

\frac{10 π}{2 π} : 5

\frac{10 π}{2 π}

消掉

\frac{10 π}{2 π} : 5

\frac{10 π}{2 π}

数字相除:

\frac{10}{2} = 5

= \frac{5 π}{π}

约分:

π

= 5

= 5

= 5 - \frac{5 arccos ( - \frac{1}{3} )}{2 π} + \frac{10 πn}{2 π}

消掉

\frac{10 πn}{2 π} : 5 n

\frac{10 πn}{2 π}

消掉

\frac{10 πn}{2 π} : 5 n

\frac{10 πn}{2 π}

数字相除:

\frac{10}{2} = 5

= \frac{5 πn}{π}

约分:

π

= 5 n

= 5 n

= 5 - \frac{5 arccos ( - \frac{1}{3} )}{2 π} + 5 n

x + 1 \leq 5 - \frac{5 arccos ( - \frac{1}{3} )}{2 π} + 5 n

x + 1 \leq 5 - \frac{5 arccos ( - \frac{1}{3} )}{2 π} + 5 n

x + 1 \leq 5 - \frac{5 arccos ( - \frac{1}{3} )}{2 π} + 5 n

将

1

到右边

x + 1 \leq 5 - \frac{5 arccos ( - \frac{1}{3} )}{2 π} + 5 n

两边减去

1

x + 1 - 1 \leq 5 - \frac{5 arccos ( - \frac{1}{3} )}{2 π} + 5 n - 1

化简

x + 1 - 1 \leq 5 - \frac{5 arccos ( - \frac{1}{3} )}{2 π} + 5 n - 1

化简

x + 1 - 1 : x

x + 1 - 1

同类项相加:

1 - 1 \leq 0

= x

化简

5 - \frac{5 arccos ( - \frac{1}{3} )}{2 π} + 5 n - 1 : 5 n + 4 - \frac{5 arccos ( - \frac{1}{3} )}{2 π}

5 - \frac{5 arccos ( - \frac{1}{3} )}{2 π} + 5 n - 1

数字相减:

5 - 1 = 4

= 5 n + 4 - \frac{5 arccos ( - \frac{1}{3} )}{2 π}

x \leq 5 n + 4 - \frac{5 arccos ( - \frac{1}{3} )}{2 π}

x \leq 5 n + 4 - \frac{5 arccos ( - \frac{1}{3} )}{2 π}

x \leq 5 n + 4 - \frac{5 arccos ( - \frac{1}{3} )}{2 π}

化简

4 - \frac{5 arccos ( - \frac{1}{3} )}{2 π} : \frac{8 π - 5 arccos ( - \frac{1}{3} )}{2 π}

4 - \frac{5 arccos ( - \frac{1}{3} )}{2 π}

将项转换为分式:

4 = \frac{4 \cdot 2 π}{2 π}

= \frac{4 \cdot 2 π}{2 π} - \frac{5 arccos ( - \frac{1}{3} )}{2 π}

因为分母相等，所以合并分式:

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{4 \cdot 2 π - 5 arccos ( - \frac{1}{3} )}{2 π}

数字相乘:

4 \cdot 2 = 8

= \frac{8 π - 5 arccos ( - \frac{1}{3} )}{2 π}

x \leq \frac{8 π - 5 arccos ( - \frac{1}{3} )}{2 π} + 5 n

合并区间

x \geq \frac{5 arccos ( - \frac{1}{3} ) - 2 π}{2 π} + 5 n and x \leq \frac{8 π - 5 arccos ( - \frac{1}{3} )}{2 π} + 5 n

合并重叠的区间

\frac{5 arccos ( - \frac{1}{3} ) - 2 π}{2 π} + 5 n \leq x \leq \frac{8 π - 5 arccos ( - \frac{1}{3} )}{2 π} + 5 n

流行的例子

cos^2(x)>= sin^2(x)

cos^{2} (x) \geq sin^{2} (x)

cos (x) > 2

sqrt(3)cos(x)+sin(x)<0

3 cos (x) + sin (x) < 0

3sqrt(3)cos(x)-13/2 <-2

33 cos (x) - \frac{13}{2} < - 2

sin(a)-cos(a)>0

sin (a) - cos (a) > 0