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受欢迎的三角函数 >

sin(2x)sec(x)+2cos(x)=0

解答

sin (2 x) sec (x) + 2 cos (x) = 0

解答

x = \frac{3 π}{4} + πn

+1

度数

x = 13 5^{\circ} + 18 0^{\circ} n

求解步骤

sin (2 x) sec (x) + 2 cos (x) = 0

使用三角恒等式改写

2 cos (x) + sec (x) sin (2 x)

使用倍角公式:

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

= 2 cos (x) + sec (x) \cdot 2 sin (x) cos (x)

2 cos (x) + 2 cos (x) sec (x) sin (x) = 0

分解

2 cos (x) + 2 cos (x) sec (x) sin (x) : 2 cos (x) (1 + sec (x) sin (x))

2 cos (x) + 2 cos (x) sec (x) sin (x)

改写为

= 1 \cdot 2 cos (x) + 2 cos (x) sec (x) sin (x)

因式分解出通项

2 cos (x)

= 2 cos (x) (1 + sec (x) sin (x))

2 cos (x) (1 + sec (x) sin (x)) = 0

分别求解每个部分

cos (x) = 0 or 1 + sec (x) sin (x) = 0

cos (x) = 0 : x = \frac{π}{2} + 2 πn, x = \frac{3 π}{2} + 2 πn

cos (x) = 0

cos (x) = 0

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}{2} + 2 πn, x = \frac{3 π}{2} + 2 πn

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

1 + sec (x) sin (x) = 0 : x = \frac{3 π}{4} + πn

1 + sec (x) sin (x) = 0

使用三角恒等式改写

1 + sec (x) sin (x)

sec (x) sin (x) = tan (x)

sec (x) sin (x)

用 sin, cos 表示

sec (x) sin (x)

使用基本三角恒等式:

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

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

化简

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

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

分式相乘:

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

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

乘以:

1 \cdot sin (x) = sin (x)

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

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

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

使用基本三角恒等式:

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

= tan (x)

= 1 + tan (x)

1 + tan (x) = 0

将

1

到右边

1 + tan (x) = 0

两边减去

1

1 + tan (x) - 1 = 0 - 1

化简

tan (x) = - 1

tan (x) = - 1

tan (x) = - 1

的通解

tan (x)

周期表（周期为

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} tan (x) 0 \frac{3}{3} 13 \pm \infty - 3 - 1 - \frac{3}{3}

x = \frac{3 π}{4} + πn

x = \frac{3 π}{4} + πn

合并所有解

x = \frac{π}{2} + 2 πn, x = \frac{3 π}{2} + 2 πn, x = \frac{3 π}{4} + πn

因为方程对以下值无定义:

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

x = \frac{3 π}{4} + πn

作图

流行的例子

sqrt(3)+2sin(x)=0

3 + 2 sin (x) = 0

tan (x) = \frac{6}{4}

cot(x)sin^2(x)=4cot(x)

cot (x) sin^{2} (x) = 4 cot (x)

solvefor x,sin(x)+cos(y)=sin(x)cos(y)

so l v e f or x, sin (x) + cos (y) = sin (x) cos (y)

solvefor x,z=arctan(x/y)

so l v e f or x, z = arctan (\frac{x}{y})