cos(θ)=-3/(sqrt(5))

解答

cos (θ) = - \frac{3}{5}

θ \in R 无解

求解步骤

cos (θ) = - \frac{3}{5}

化简

- \frac{3}{5} : - \frac{3 5}{5}

- \frac{3}{5}

乘以共轭根式

\frac{5}{5}

= - \frac{3 5}{5 5}

55 = 5

55

使用根式运算法则:

a a = a

55 = 5

= 5

= - \frac{3 5}{5}

cos (θ) = - \frac{3 5}{5}

- 1 \leq cos (x) \leq 1

θ \in R 无解

2 sec (x) + tan^{2} (x) - 9 = 1

sin (x) = 1.34

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

6 - 9 sin (θ) - 4 cos^{2} (θ) = 0

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