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受欢迎的三角函数 >

4cos(x)=4-4cos(x)

解答

4 cos (x) = 4 - 4 cos (x)

解答

x = \frac{π}{3} + 2 πn, x = \frac{5 π}{3} + 2 πn

+1

度数

x = 6 0^{\circ} + 36 0^{\circ} n, x = 30 0^{\circ} + 36 0^{\circ} n

求解步骤

4 cos (x) = 4 - 4 cos (x)

用替代法求解

4 cos (x) = 4 - 4 cos (x)

令

: cos (x) = u

4 u = 4 - 4 u

4 u = 4 - 4 u : u = \frac{1}{2}

4 u = 4 - 4 u

将

4 u

para o lado esquerdo

4 u = 4 - 4 u

两边加上

4 u

4 u + 4 u = 4 - 4 u + 4 u

化简

8 u = 4

8 u = 4

两边除以

8

8 u = 4

两边除以

8

\frac{8 u}{8} = \frac{4}{8}

化简

u = \frac{1}{2}

u = \frac{1}{2}

u = cos (x)

代回

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

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

cos (x) = \frac{1}{2} : x = \frac{π}{3} + 2 πn, x = \frac{5 π}{3} + 2 πn

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

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

的通解

cos (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} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{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} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

x = \frac{π}{3} + 2 πn, x = \frac{5 π}{3} + 2 πn

x = \frac{π}{3} + 2 πn, x = \frac{5 π}{3} + 2 πn

合并所有解

x = \frac{π}{3} + 2 πn, x = \frac{5 π}{3} + 2 πn

作图

流行的例子

cos(2x)-cos(6x)-sin(4x)=0,0<= x<= pi

cos (2 x) - cos (6 x) - sin (4 x) = 0, 0 \leq x \leq π

0 = 3 sin (θ)

2cos^2(x)+sin(x)-1=0,(0,2pi)

2 cos^{2} (x) + sin (x) - 1 = 0, (0, 2 π)

4cos^2(x)-2cos(x)-1=0

4 cos^{2} (x) - 2 cos (x) - 1 = 0

cos^2(x)-4cos(x)-5=0

cos^{2} (x) - 4 cos (x) - 5 = 0