cos(x)=-0.2

解答

cos (x) = - 0.2

x = 1.77215 \dots + 2 πn, x = - 1.77215 \dots + 2 πn

度数

x = 101.53695 \dots^{\circ} + 36 0^{\circ} n, x = - 101.53695 \dots^{\circ} + 36 0^{\circ} n

求解步骤

cos (x) = - 0.2

使用反三角函数性质

cos (x) = - 0.2

cos (x) = - 0.2

的通解

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

x = arccos (- 0.2) + 2 πn, x = - arccos (- 0.2) + 2 πn

x = arccos (- 0.2) + 2 πn, x = - arccos (- 0.2) + 2 πn

以小数形式表示解

x = 1.77215 \dots + 2 πn, x = - 1.77215 \dots + 2 πn

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

2 sin (x) - cos (2 x) = 0

sin^{2} (x) sec (x) = tan^{2} (x)

cos (2 x + \frac{π}{3}) = - \frac{1}{2}

sec (θ + 2 0^{\circ}) = 3