Question

How to solve these two problems ？

Answer 1

8)  $\theta$ is -0.896 radians

9) length of arc is 41.91 cm

Solution:

8)

Given that,

$tan\ \theta = \frac{-5}{4}$

$\theta$ is in quadrant 4

To find: $\theta$

From given,

$tan\ \theta = \frac{-5}{4}\\\\\theta = tan^{-1} \frac{-5}{4}\\\\\theta = tan^{-1} (-1.25)\\\\\theta = -51.34$

Thus value of $\theta$ is -51.34 degrees

Convert degrees to radians

$-51.34\ degree = -51.34 \times \frac{ \pi }{180}\ radian\\\\-51.34\ degree = -0.896\ radian$

Thus $\theta$ is -0.896 radians

9)

From given,

radius = 15.4 cm

$\theta = \frac{13 \pi }{15}$

The length of arc when angle in radians is:

$arc\ length = r \times \theta\\\\arc\ length = 15.4 \times \frac{ 13 \pi }{15}\\\\arc\ length = 15.4 \times 2.721\\\\arc\ length = 41.91$

Thus length of arc is 41.91 cm