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受欢迎的三角函数 >

3tan^2(x)=2sec^2(x)+1,0<= x<= 180

解答

3 tan^{2} (x) = 2 sec^{2} (x) + 1, 0^{\circ} \leq x \leq 18 0^{\circ}

解答

x = 6 0^{\circ}, x = 12 0^{\circ}

+1

弧度

x = \frac{π}{3}, x = \frac{2 π}{3}

求解步骤

3 tan^{2} (x) = 2 sec^{2} (x) + 1, 0^{\circ} \leq x \leq 18 0^{\circ}

两边减去

2 sec^{2} (x) + 1

3 tan^{2} (x) - 2 sec^{2} (x) - 1 = 0

使用三角恒等式改写

- 1 - 2 sec^{2} (x) + 3 tan^{2} (x)

使用毕达哥拉斯恒等式:

tan^{2} (x) + 1 = sec^{2} (x)

tan^{2} (x) = sec^{2} (x) - 1

= - 1 - 2 sec^{2} (x) + 3 (sec^{2} (x) - 1)

化简

- 1 - 2 sec^{2} (x) + 3 (sec^{2} (x) - 1) : sec^{2} (x) - 4

- 1 - 2 sec^{2} (x) + 3 (sec^{2} (x) - 1)

乘开

3 (sec^{2} (x) - 1) : 3 sec^{2} (x) - 3

3 (sec^{2} (x) - 1)

使用分配律:

a (b - c) = ab - a c

a = 3, b = sec^{2} (x), c = 1

= 3 sec^{2} (x) - 3 \cdot 1

数字相乘:

3 \cdot 1 = 3

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

= - 1 - 2 sec^{2} (x) + 3 sec^{2} (x) - 3

化简

- 1 - 2 sec^{2} (x) + 3 sec^{2} (x) - 3 : sec^{2} (x) - 4

- 1 - 2 sec^{2} (x) + 3 sec^{2} (x) - 3

同类项相加:

- 2 sec^{2} (x) + 3 sec^{2} (x) = sec^{2} (x)

= - 1 + sec^{2} (x) - 3

对同类项分组

= sec^{2} (x) - 1 - 3

数字相减:

- 1 - 3 = - 4

= sec^{2} (x) - 4

= sec^{2} (x) - 4

= sec^{2} (x) - 4

- 4 + sec^{2} (x) = 0

用替代法求解

- 4 + sec^{2} (x) = 0

令

: sec (x) = u

- 4 + u^{2} = 0

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

- 4 + u^{2} = 0

将

4

到右边

- 4 + u^{2} = 0

两边加上

4

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

化简

u^{2} = 4

u^{2} = 4

对于

x^{2} = f (a)

解为

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

u = 4, u = - 4

4 = 2

4

因式分解数字:

4 = 2^{2}

= 2^{2}

使用根式运算法则:

n a^{n} = a

2^{2} = 2

= 2

- 4 = - 2

- 4

4 = 2

4

因式分解数字:

4 = 2^{2}

= 2^{2}

使用根式运算法则:

n a^{n} = a

2^{2} = 2

= 2

= - 2

u = 2, u = - 2

u = sec (x)

代回

sec (x) = 2, sec (x) = - 2

sec (x) = 2, sec (x) = - 2

sec (x) = 2, 0 \leq x \leq 18 0^{\circ} : x = 6 0^{\circ}

sec (x) = 2, 0 \leq x \leq 18 0^{\circ}

sec (x) = 2

的通解

sec (x)

周期表（周期为

36 0^{\circ} n

）：

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} sec (x) 1 \frac{2 3}{3} 22 Undefined - 2 - 2 - \frac{2 3}{3} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} sec (x) - 1 - \frac{2 3}{3} - 2 - 2 Undefined 22 \frac{2 3}{3}

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

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

在

0 \leq x \leq 18 0^{\circ}

范围内的解

x = 6 0^{\circ}

sec (x) = - 2, 0 \leq x \leq 18 0^{\circ} : x = 12 0^{\circ}

sec (x) = - 2, 0 \leq x \leq 18 0^{\circ}

sec (x) = - 2

的通解

sec (x)

周期表（周期为

36 0^{\circ} n

）：

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} sec (x) 1 \frac{2 3}{3} 22 Undefined - 2 - 2 - \frac{2 3}{3} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} sec (x) - 1 - \frac{2 3}{3} - 2 - 2 Undefined 22 \frac{2 3}{3}

x = 12 0^{\circ} + 36 0^{\circ} n, x = 24 0^{\circ} + 36 0^{\circ} n

x = 12 0^{\circ} + 36 0^{\circ} n, x = 24 0^{\circ} + 36 0^{\circ} n

在

0 \leq x \leq 18 0^{\circ}

范围内的解

x = 12 0^{\circ}

合并所有解

x = 6 0^{\circ}, x = 12 0^{\circ}

作图

流行的例子

solvefor x,2cos(x)-sqrt(2)=0

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cos (x) = \frac{2.16}{3.42}

sinh(x)= 5/12 ,cosh(x)

sinh (x) = \frac{5}{12}, cosh (x)

sin (x) = cos (1 9^{\circ})

tan (A) = \frac{8}{15}