zs

English

Español

Português

Français

Deutsch

Italiano

Русский

中文(简体)

한국어

日本語

Tiếng Việt

עברית

العربية

受欢迎的三角函数 >

sqrt(8)cos(θ)+7=-6cos(θ)+sqrt(5)

解答

8 cos (θ) + 7 = - 6 cos (θ) + 5

解答

θ = 2.14077 \dots + 2 πn, θ = - 2.14077 \dots + 2 πn

+1

度数

θ = 122.65728 \dots^{\circ} + 36 0^{\circ} n, θ = - 122.65728 \dots^{\circ} + 36 0^{\circ} n

求解步骤

8 cos (θ) + 7 = - 6 cos (θ) + 5

用替代法求解

8 cos (θ) + 7 = - 6 cos (θ) + 5

令

: cos (θ) = u

8 u + 7 = - 6 u + 5

8 u + 7 = - 6 u + 5 : u = \frac{( 5 - 7 ) ( 3 - 2 )}{14}

8 u + 7 = - 6 u + 5

化简

8 u + 7 : 22 u + 7

8 u + 7

8 = 22

8

8

质因数分解:

2^{3}

8

8

除以

28 = 4 \cdot 2

= 2 \cdot 4

4

除以

24 = 2 \cdot 2

= 2 \cdot 2 \cdot 2

2

是质数，因此无法进一步因数分解

= 2 \cdot 2 \cdot 2

= 2^{3}

= 2^{3}

使用指数法则:

a^{b + c} = a^{b} \cdot a^{c}

= 2^{2} \cdot 2

使用根式运算法则:

n ab = n a n b

= 2 2^{2}

使用根式运算法则:

n a^{n} = a

2^{2} = 2

= 22

= 22 u + 7

22 u + 7 = - 6 u + 5

将

7

到右边

22 u + 7 = - 6 u + 5

两边减去

7

22 u + 7 - 7 = - 6 u + 5 - 7

化简

22 u = - 6 u + 5 - 7

22 u = - 6 u + 5 - 7

将

6 u

para o lado esquerdo

22 u = - 6 u + 5 - 7

两边加上

6 u

22 u + 6 u = - 6 u + 5 - 7 + 6 u

化简

22 u + 6 u = 5 - 7

22 u + 6 u = 5 - 7

分解

22 u + 6 u : 2 (2 + 3) u

22 u + 6 u

改写为

= 2 u 2 + 3 \cdot 2 u

因式分解出通项

2 u

= 2 u (2 + 3)

2 (2 + 3) u = 5 - 7

两边除以

2 (2 + 3)

2 (2 + 3) u = 5 - 7

两边除以

2 (2 + 3)

\frac{2 ( 2 + 3 ) u}{2 ( 2 + 3 )} = \frac{5}{2 ( 2 + 3 )} - \frac{7}{2 ( 2 + 3 )}

化简

\frac{2 ( 2 + 3 ) u}{2 ( 2 + 3 )} = \frac{5}{2 ( 2 + 3 )} - \frac{7}{2 ( 2 + 3 )}

化简

\frac{2 ( 2 + 3 ) u}{2 ( 2 + 3 )} : u

\frac{2 ( 2 + 3 ) u}{2 ( 2 + 3 )}

数字相除:

\frac{2}{2} = 1

= \frac{( 3 + 2 ) u}{( 2 + 3 )}

约分:

2 + 3

= u

化简

\frac{5}{2 ( 2 + 3 )} - \frac{7}{2 ( 2 + 3 )} : \frac{( 5 - 7 ) ( 3 - 2 )}{14}

\frac{5}{2 ( 2 + 3 )} - \frac{7}{2 ( 2 + 3 )}

使用法则

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

= \frac{5 - 7}{2 ( 3 + 2 )}

乘以共轭根式

\frac{3 - 2}{3 - 2}

= \frac{( 5 - 7 ) ( 3 - 2 )}{2 ( 3 + 2 ) ( 3 - 2 )}

2 (3 + 2) (3 - 2) = 14

2 (3 + 2) (3 - 2)

乘开

(3 + 2) (3 - 2) : 7

(3 + 2) (3 - 2)

使用平方差公式:

(a + b) (a - b) = a^{2} - b^{2}

a = 3, b = 2

= 3^{2} - (2)^{2}

化简

3^{2} - (2)^{2} : 7

3^{2} - (2)^{2}

3^{2} = 9

3^{2}

3^{2} = 9

= 9

(2)^{2} = 2

(2)^{2}

使用根式运算法则:

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

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

使用指数法则:

(a^{b})^{c} = a^{b c}

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

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

\frac{1}{2} \cdot 2

分式相乘:

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

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

约分:

2

= 1

= 2

= 9 - 2

数字相减:

9 - 2 = 7

= 7

= 7

= 2 \cdot 7

乘开

2 \cdot 7 : 14

2 \cdot 7

打开括号

= 2 \cdot 7

数字相乘:

2 \cdot 7 = 14

= 14

= 14

= \frac{( 5 - 7 ) ( 3 - 2 )}{14}

u = \frac{( 5 - 7 ) ( 3 - 2 )}{14}

u = \frac{( 5 - 7 ) ( 3 - 2 )}{14}

u = \frac{( 5 - 7 ) ( 3 - 2 )}{14}

u = cos (θ)

代回

cos (θ) = \frac{( 5 - 7 ) ( 3 - 2 )}{14}

cos (θ) = \frac{( 5 - 7 ) ( 3 - 2 )}{14}

cos (θ) = \frac{( 5 - 7 ) ( 3 - 2 )}{14} : θ = arccos (\frac{( 5 - 7 ) ( 3 - 2 )}{14}) + 2 πn, θ = - arccos (\frac{( 5 - 7 ) ( 3 - 2 )}{14}) + 2 πn

cos (θ) = \frac{( 5 - 7 ) ( 3 - 2 )}{14}

使用反三角函数性质

cos (θ) = \frac{( 5 - 7 ) ( 3 - 2 )}{14}

cos (θ) = \frac{( 5 - 7 ) ( 3 - 2 )}{14}

的通解

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

θ = arccos (\frac{( 5 - 7 ) ( 3 - 2 )}{14}) + 2 πn, θ = - arccos (\frac{( 5 - 7 ) ( 3 - 2 )}{14}) + 2 πn

θ = arccos (\frac{( 5 - 7 ) ( 3 - 2 )}{14}) + 2 πn, θ = - arccos (\frac{( 5 - 7 ) ( 3 - 2 )}{14}) + 2 πn

合并所有解

θ = arccos (\frac{( 5 - 7 ) ( 3 - 2 )}{14}) + 2 πn, θ = - arccos (\frac{( 5 - 7 ) ( 3 - 2 )}{14}) + 2 πn

以小数形式表示解

θ = 2.14077 \dots + 2 πn, θ = - 2.14077 \dots + 2 πn

作图

流行的例子

8sin(θ)+15cos(θ)=17

8 sin (θ) + 15 cos (θ) = 17

cos (x - 1) = 0

2sin(t)+3cos(t)=0

2 sin (t) + 3 cos (t) = 0

tan(θ)=(-11/3-(-4/3))/(1+(-4/3)(-11/3))

tan (θ) = \frac{- \frac{11}{3} - ( - \frac{4}{3} )}{1 + ( - \frac{4}{3} ) ( - \frac{11}{3} )}

csc(2x)=2,x0<x<360

csc (2 x) = 2, x 0^{\circ} < x < 36 0^{\circ}