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受欢迎的三角函数 >

sin(x)-cos(x)= 1/3 ,sin(2x)

解答

sin (x) - cos (x) = \frac{1}{3}, sin (2 x)

解答

x \in R 无解

求解步骤

sin (x) - cos (x) = \frac{1}{3}, sin (2 x)

使用三角恒等式改写

sin (x) - cos (x)

sin (x) - cos (x) = 2 sin (x - \frac{π}{4})

sin (x) - cos (x)

改写为

= 2 (\frac{1}{2} sin (x) - \frac{1}{2} cos (x))

使用以下普通恒等式:

cos (\frac{π}{4}) = \frac{1}{2}

使用以下普通恒等式:

sin (\frac{π}{4}) = \frac{1}{2}

= 2 (cos (\frac{π}{4}) sin (x) - sin (\frac{π}{4}) cos (x))

使用角和恒等式:

sin (s - t) = sin (s) cos (t) - cos (s) sin (t)

= 2 sin (x - \frac{π}{4})

= 2 sin (x - \frac{π}{4})

2 sin (x - \frac{π}{4}) = \frac{1}{3}

两边除以

2

2 sin (x - \frac{π}{4}) = \frac{1}{3}

两边除以

2

\frac{2 sin ( x - \frac{π}{4} )}{2} = \frac{\frac{1}{3}}{2}

化简

\frac{2 sin ( x - \frac{π}{4} )}{2} = \frac{\frac{1}{3}}{2}

化简

\frac{2 sin ( x - \frac{π}{4} )}{2} : sin (x - \frac{π}{4})

\frac{2 sin ( x - \frac{π}{4} )}{2}

约分:

2

= sin (x - \frac{π}{4})

化简

\frac{\frac{1}{3}}{2} : \frac{2}{6}

\frac{\frac{1}{3}}{2}

使用分式法则:

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

= \frac{1}{3 2}

\frac{1}{3 2}

有理化:

\frac{2}{6}

\frac{1}{3 2}

乘以共轭根式

\frac{2}{2}

= \frac{1 \cdot 2}{3 2 2}

1 \cdot 2 = 2

322 = 6

322

使用根式运算法则:

a a = a

22 = 2

= 3 \cdot 2

数字相乘:

3 \cdot 2 = 6

= 6

= \frac{2}{6}

= \frac{2}{6}

sin (x - \frac{π}{4}) = \frac{2}{6}

sin (x - \frac{π}{4}) = \frac{2}{6}

sin (x - \frac{π}{4}) = \frac{2}{6}

使用反三角函数性质

sin (x - \frac{π}{4}) = \frac{2}{6}

sin (x - \frac{π}{4}) = \frac{2}{6}

的通解

sin (x) = a \Rightarrow x = arcsin (a) + 2 πn, x = π - arcsin (a) + 2 πn

x - \frac{π}{4} = arcsin (\frac{2}{6}) + 2 πn, x - \frac{π}{4} = π - arcsin (\frac{2}{6}) + 2 πn

x - \frac{π}{4} = arcsin (\frac{2}{6}) + 2 πn, x - \frac{π}{4} = π - arcsin (\frac{2}{6}) + 2 πn

解

x - \frac{π}{4} = arcsin (\frac{2}{6}) + 2 πn : x = arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

x - \frac{π}{4} = arcsin (\frac{2}{6}) + 2 πn

化简

arcsin (\frac{2}{6}) + 2 πn : arcsin (\frac{1}{3 2}) + 2 πn

arcsin (\frac{2}{6}) + 2 πn

\frac{2}{6} = \frac{1}{3 2}

\frac{2}{6}

分解

6 : 2 \cdot 3

因式分解

6 = 2 \cdot 3

= \frac{2}{2 \cdot 3}

消掉

\frac{2}{2 \cdot 3} : \frac{1}{2 \cdot 3}

\frac{2}{2 \cdot 3}

使用根式运算法则:

n a = a^{\frac{1}{n}}

2 = 2^{\frac{1}{2}}

= \frac{2 ^{\frac{1}{2}}}{2 \cdot 3}

使用指数法则:

\frac{x ^{a}}{x ^{b}} = \frac{1}{x ^{b - a}}

\frac{2 ^{\frac{1}{2}}}{2 ^{1}} = \frac{1}{2 ^{1 - \frac{1}{2}}}

= \frac{1}{3 \cdot 2 ^{- \frac{1}{2} + 1}}

数字相减:

1 - \frac{1}{2} = \frac{1}{2}

= \frac{1}{3 \cdot 2 ^{\frac{1}{2}}}

使用根式运算法则:

a^{\frac{1}{n}} = n a

2^{\frac{1}{2}} = 2

= \frac{1}{3 2}

= \frac{1}{2 \cdot 3}

= arcsin (\frac{1}{3 2}) + 2 πn

x - \frac{π}{4} = arcsin (\frac{1}{3 2}) + 2 πn

将

\frac{π}{4}

到右边

x - \frac{π}{4} = arcsin (\frac{1}{3 2}) + 2 πn

两边加上

\frac{π}{4}

x - \frac{π}{4} + \frac{π}{4} = arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

化简

x - \frac{π}{4} + \frac{π}{4} = arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

化简

x - \frac{π}{4} + \frac{π}{4} : x

x - \frac{π}{4} + \frac{π}{4}

同类项相加:

- \frac{π}{4} + \frac{π}{4} = 0

= x

化简

arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4} : arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

= arcsin (\frac{2}{6}) + 2 πn + \frac{π}{4}

\frac{2}{6} = \frac{1}{3 2}

\frac{2}{6}

分解

6 : 2 \cdot 3

因式分解

6 = 2 \cdot 3

= \frac{2}{2 \cdot 3}

消掉

\frac{2}{2 \cdot 3} : \frac{1}{2 \cdot 3}

\frac{2}{2 \cdot 3}

使用根式运算法则:

n a = a^{\frac{1}{n}}

2 = 2^{\frac{1}{2}}

= \frac{2 ^{\frac{1}{2}}}{2 \cdot 3}

使用指数法则:

\frac{x ^{a}}{x ^{b}} = \frac{1}{x ^{b - a}}

\frac{2 ^{\frac{1}{2}}}{2 ^{1}} = \frac{1}{2 ^{1 - \frac{1}{2}}}

= \frac{1}{3 \cdot 2 ^{- \frac{1}{2} + 1}}

数字相减:

1 - \frac{1}{2} = \frac{1}{2}

= \frac{1}{3 \cdot 2 ^{\frac{1}{2}}}

使用根式运算法则:

a^{\frac{1}{n}} = n a

2^{\frac{1}{2}} = 2

= \frac{1}{3 2}

= \frac{1}{2 \cdot 3}

= arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

无法进一步化简

= arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

x = arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

x = arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

x = arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

解

x - \frac{π}{4} = π - arcsin (\frac{2}{6}) + 2 πn : x = π - arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

x - \frac{π}{4} = π - arcsin (\frac{2}{6}) + 2 πn

化简

π - arcsin (\frac{2}{6}) + 2 πn : π - arcsin (\frac{1}{3 2}) + 2 πn

π - arcsin (\frac{2}{6}) + 2 πn

\frac{2}{6} = \frac{1}{3 2}

\frac{2}{6}

分解

6 : 2 \cdot 3

因式分解

6 = 2 \cdot 3

= \frac{2}{2 \cdot 3}

消掉

\frac{2}{2 \cdot 3} : \frac{1}{2 \cdot 3}

\frac{2}{2 \cdot 3}

使用根式运算法则:

n a = a^{\frac{1}{n}}

2 = 2^{\frac{1}{2}}

= \frac{2 ^{\frac{1}{2}}}{2 \cdot 3}

使用指数法则:

\frac{x ^{a}}{x ^{b}} = \frac{1}{x ^{b - a}}

\frac{2 ^{\frac{1}{2}}}{2 ^{1}} = \frac{1}{2 ^{1 - \frac{1}{2}}}

= \frac{1}{3 \cdot 2 ^{- \frac{1}{2} + 1}}

数字相减:

1 - \frac{1}{2} = \frac{1}{2}

= \frac{1}{3 \cdot 2 ^{\frac{1}{2}}}

使用根式运算法则:

a^{\frac{1}{n}} = n a

2^{\frac{1}{2}} = 2

= \frac{1}{3 2}

= \frac{1}{2 \cdot 3}

= π - arcsin (\frac{1}{3 2}) + 2 πn

x - \frac{π}{4} = π - arcsin (\frac{1}{3 2}) + 2 πn

将

\frac{π}{4}

到右边

x - \frac{π}{4} = π - arcsin (\frac{1}{3 2}) + 2 πn

两边加上

\frac{π}{4}

x - \frac{π}{4} + \frac{π}{4} = π - arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

化简

x - \frac{π}{4} + \frac{π}{4} = π - arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

化简

x - \frac{π}{4} + \frac{π}{4} : x

x - \frac{π}{4} + \frac{π}{4}

同类项相加:

- \frac{π}{4} + \frac{π}{4} = 0

= x

化简

π - arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4} : π - arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

π - arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

= π - arcsin (\frac{2}{6}) + 2 πn + \frac{π}{4}

\frac{2}{6} = \frac{1}{3 2}

\frac{2}{6}

分解

6 : 2 \cdot 3

因式分解

6 = 2 \cdot 3

= \frac{2}{2 \cdot 3}

消掉

\frac{2}{2 \cdot 3} : \frac{1}{2 \cdot 3}

\frac{2}{2 \cdot 3}

使用根式运算法则:

n a = a^{\frac{1}{n}}

2 = 2^{\frac{1}{2}}

= \frac{2 ^{\frac{1}{2}}}{2 \cdot 3}

使用指数法则:

\frac{x ^{a}}{x ^{b}} = \frac{1}{x ^{b - a}}

\frac{2 ^{\frac{1}{2}}}{2 ^{1}} = \frac{1}{2 ^{1 - \frac{1}{2}}}

= \frac{1}{3 \cdot 2 ^{- \frac{1}{2} + 1}}

数字相减:

1 - \frac{1}{2} = \frac{1}{2}

= \frac{1}{3 \cdot 2 ^{\frac{1}{2}}}

使用根式运算法则:

a^{\frac{1}{n}} = n a

2^{\frac{1}{2}} = 2

= \frac{1}{3 2}

= \frac{1}{2 \cdot 3}

= π - arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

无法进一步化简

= π - arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

x = π - arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

x = π - arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

x = π - arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

x = arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}, x = π - arcsin (\frac{1}{3 2}) + 2 πn + \frac{π}{4}

在

sin (2 x)

范围内的解

x \in R 无解

作图

流行的例子

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arctan (θ) = \frac{2}{2 3}

3sin(x)=+sin(x)

3 sin (x) = + sin (x)

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