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受欢迎的三角函数 >

tan(x)+2cos(x)csc(x)=sec(x)cos(x)+cot(x)

解答

tan (x) + 2 cos (x) csc (x) = sec (x) cos (x) + cot (x)

解答

x \in R 无解

求解步骤

tan (x) + 2 cos (x) csc (x) = sec (x) cos (x) + cot (x)

两边减去

sec (x) cos (x) + cot (x)

tan (x) + 2 cos (x) csc (x) - sec (x) cos (x) - cot (x) = 0

用 sin, cos 表示

- cot (x) + tan (x) - cos (x) sec (x) + 2 cos (x) csc (x)

使用基本三角恒等式:

cot (x) = \frac{cos ( x )}{sin ( x )}

= - \frac{cos ( x )}{sin ( x )} + tan (x) - cos (x) sec (x) + 2 cos (x) csc (x)

使用基本三角恒等式:

tan (x) = \frac{sin ( x )}{cos ( x )}

= - \frac{cos ( x )}{sin ( x )} + \frac{sin ( x )}{cos ( x )} - cos (x) sec (x) + 2 cos (x) csc (x)

使用基本三角恒等式:

sec (x) = \frac{1}{cos ( x )}

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

使用基本三角恒等式:

csc (x) = \frac{1}{sin ( x )}

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

化简

- \frac{cos ( x )}{sin ( x )} + \frac{sin ( x )}{cos ( x )} - cos (x) \frac{1}{cos ( x )} + 2 cos (x) \frac{1}{sin ( x )} : \frac{cos ^{2} ( x ) + sin ^{2} ( x ) - sin ( x ) cos ( x )}{sin ( x ) cos ( x )}

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

cos (x) \frac{1}{cos ( x )} = 1

cos (x) \frac{1}{cos ( x )}

分式相乘:

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

= \frac{1 \cdot cos ( x )}{cos ( x )}

约分:

cos (x)

= 1

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

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

分式相乘:

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

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

数字相乘:

1 \cdot 2 = 2

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

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

合并分式

- \frac{cos ( x )}{sin ( x )} + \frac{2 cos ( x )}{sin ( x )} : \frac{cos ( x )}{sin ( x )}

使用法则

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

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

同类项相加:

- cos (x) + 2 cos (x) = cos (x)

= \frac{cos ( x )}{sin ( x )}

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

将项转换为分式:

1 = \frac{1}{1}

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

sin (x), cos (x), 1

的最小公倍数:

sin (x) cos (x)

sin (x), cos (x), 1

最小公倍数 (LCM)

计算出由至少在以下一个因式表达式中出现的因子组成的表达式

= sin (x) cos (x)

根据最小公倍数调整分式

将每个分子乘以其分母转变为最小公倍数所要乘以的同一数值

sin (x) cos (x)

对于

\frac{cos ( x )}{sin ( x )} :

将分母和分子乘以

cos (x)

\frac{cos ( x )}{sin ( x )} = \frac{cos ( x ) cos ( x )}{sin ( x ) cos ( x )} = \frac{cos ^{2} ( x )}{sin ( x ) cos ( x )}

对于

\frac{sin ( x )}{cos ( x )} :

将分母和分子乘以

sin (x)

\frac{sin ( x )}{cos ( x )} = \frac{sin ( x ) sin ( x )}{cos ( x ) sin ( x )} = \frac{sin ^{2} ( x )}{sin ( x ) cos ( x )}

对于

\frac{1}{1} :

将分母和分子乘以

sin (x) cos (x)

\frac{1}{1} = \frac{1 \cdot sin ( x ) cos ( x )}{1 \cdot sin ( x ) cos ( x )} = \frac{sin ( x ) cos ( x )}{sin ( x ) cos ( x )}

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

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{cos ^{2} ( x ) + sin ^{2} ( x ) - sin ( x ) cos ( x )}{sin ( x ) cos ( x )}

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

\frac{cos ^{2} ( x ) + sin ^{2} ( x ) - cos ( x ) sin ( x )}{cos ( x ) sin ( x )} = 0

\frac{f ( x )}{g ( x )} = 0 \Rightarrow f (x) = 0

cos^{2} (x) + sin^{2} (x) - cos (x) sin (x) = 0

使用三角恒等式改写

- cos (x) sin (x) + 1

使用倍角公式:

2 sin (x) cos (x) = sin (2 x)

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

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

1 - \frac{sin ( 2 x )}{2} = 0

将

1

到右边

1 - \frac{sin ( 2 x )}{2} = 0

两边减去

1

1 - \frac{sin ( 2 x )}{2} - 1 = 0 - 1

化简

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

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

在两边乘以

2

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

在两边乘以

2

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

化简

- sin (2 x) = - 2

- sin (2 x) = - 2

两边除以

- 1

- sin (2 x) = - 2

两边除以

- 1

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

化简

sin (2 x) = 2

sin (2 x) = 2

- 1 \leq sin (x) \leq 1

x \in R 无解

作图

流行的例子

cos(a)=(sqrt(5))/5

5sec^2(x)-5=0,0<= x<2pi

5sin(y)-5=3sin(y)-4