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受欢迎的三角函数 >

sin(x)+sin^2(x)+sin^3(x)+sin^4(x)=0

解答

sin (x) + sin^{2} (x) + sin^{3} (x) + sin^{4} (x) = 0

解答

x = 2 πn, x = π + 2 πn, x = \frac{3 π}{2} + 2 πn

+1

度数

x = 0^{\circ} + 36 0^{\circ} n, x = 18 0^{\circ} + 36 0^{\circ} n, x = 27 0^{\circ} + 36 0^{\circ} n

求解步骤

sin (x) + sin^{2} (x) + sin^{3} (x) + sin^{4} (x) = 0

用替代法求解

sin (x) + sin^{2} (x) + sin^{3} (x) + sin^{4} (x) = 0

令

: sin (x) = u

u + u^{2} + u^{3} + u^{4} = 0

u + u^{2} + u^{3} + u^{4} = 0 : u = 0, u = - 1, u = i, u = - i

u + u^{2} + u^{3} + u^{4} = 0

因式分解

u + u^{2} + u^{3} + u^{4} : u (u + 1) (u^{2} + 1)

u + u^{2} + u^{3} + u^{4}

因式分解出通项

u : u (u^{3} + u^{2} + u + 1)

u^{4} + u^{3} + u^{2} + u

使用指数法则:

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

u^{2} = uu

= u^{3} u + u^{2} u + uu + u

因式分解出通项

u

= u (u^{3} + u^{2} + u + 1)

= u (u^{3} + u^{2} + u + 1)

分解

u^{3} + u^{2} + u + 1 : (u + 1) (u^{2} + 1)

u^{3} + u^{2} + u + 1

= (u^{3} + u^{2}) + (u + 1)

从

u^{3} + u^{2}

分解出因式

u^{2}

:

u^{2} (u + 1)

u^{3} + u^{2}

使用指数法则:

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

u^{3} = u u^{2}

= u u^{2} + u^{2}

因式分解出通项

u^{2}

= u^{2} (u + 1)

= (u + 1) + u^{2} (u + 1)

因式分解出通项

u + 1

= (u + 1) (u^{2} + 1)

= u (u + 1) (u^{2} + 1)

u (u + 1) (u^{2} + 1) = 0

使用零因数法则： If

ab = 0

then

a = 0

or

b = 0

u = 0 or u + 1 = 0 or u^{2} + 1 = 0

解

u + 1 = 0 : u = - 1

u + 1 = 0

将

1

到右边

u + 1 = 0

两边减去

1

u + 1 - 1 = 0 - 1

化简

u = - 1

u = - 1

解

u^{2} + 1 = 0 : u = i, u = - i

u^{2} + 1 = 0

将

1

到右边

u^{2} + 1 = 0

两边减去

1

u^{2} + 1 - 1 = 0 - 1

化简

u^{2} = - 1

u^{2} = - 1

对于

x^{2} = f (a)

解为

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

u = - 1, u = - - 1

化简

- 1 : i

- 1

使用虚数运算法则:

- 1 = i

= i

化简

- - 1 : - i

- - 1

使用虚数运算法则:

- 1 = i

= - i

u = i, u = - i

解为

u = 0, u = - 1, u = i, u = - i

u = sin (x)

代回

sin (x) = 0, sin (x) = - 1, sin (x) = i, sin (x) = - i

sin (x) = 0, sin (x) = - 1, sin (x) = i, sin (x) = - i

sin (x) = 0 : x = 2 πn, x = π + 2 πn

sin (x) = 0

sin (x) = 0

的通解

sin (x)

周期表（周期为

2 πn

"）：

x 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} \frac{2 π}{3} \frac{3 π}{4} \frac{5 π}{6} sin (x) 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} x π \frac{7 π}{6} \frac{5 π}{4} \frac{4 π}{3} \frac{3 π}{2} \frac{5 π}{3} \frac{7 π}{4} \frac{11 π}{6} sin (x) 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2}

x = 0 + 2 πn, x = π + 2 πn

x = 0 + 2 πn, x = π + 2 πn

解

x = 0 + 2 πn : x = 2 πn

x = 0 + 2 πn

0 + 2 πn = 2 πn

x = 2 πn

x = 2 πn, x = π + 2 πn

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

sin (x) = - 1

sin (x) = - 1

的通解

sin (x)

周期表（周期为

2 πn

"）：

x 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} \frac{2 π}{3} \frac{3 π}{4} \frac{5 π}{6} sin (x) 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} x π \frac{7 π}{6} \frac{5 π}{4} \frac{4 π}{3} \frac{3 π}{2} \frac{5 π}{3} \frac{7 π}{4} \frac{11 π}{6} sin (x) 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2}

x = \frac{3 π}{2} + 2 πn

x = \frac{3 π}{2} + 2 πn

sin (x) = i :

无解

sin (x) = i

无解

sin (x) = - i :

无解

sin (x) = - i

无解

合并所有解

x = 2 πn, x = π + 2 πn, x = \frac{3 π}{2} + 2 πn

作图

流行的例子

sin(9x)-cos(x)=0

sin (9 x) - cos (x) = 0

cos(x)+2cos^2(x)=1

cos (x) + 2 cos^{2} (x) = 1

solvefor t,0.08=0.1cos(4t)

so l v e f or t, 0.08 = 0.1 cos (4 t)

cos(180-x)=sin(-300)

cos (18 0^{\circ} - x) = sin (- 30 0^{\circ})

cos (θ) = 0.417