You want to erect a pole of height 10 m with the support of three ropes . Each rope has to make an angle 30 degrees with the pole. What should be the length of the rope ?
Draw a picture with one of the ropes. You have a right triangle with height = 10 m and angle at pole = 30 deg.
Now simply find the hypotenuse of the triangle. As the rope length will be equal to the hypotenuse.
Here is the equation: cos (30) = pole / hypotenuse
putting values we get √3 / 2 = 10 / hypotenuse
Therefore hypotenuse = 2 * 10 / √3 = 20 √3 / 3 ~ 11.55 meters