# Length of line projected onto a horizontal line at some angle.

Please see the image to understand my question:

Given the angle theta, and 3 parallel lines, the top line being 5 unit distances away from the middle line. How do I calculate the length of the line segment labelled ? in the image?

• $\sin$ is your friend. – Michael Hoppe Jun 9 at 12:36
• sine takes an angle in radians and returns a number between -1 and +1, how does that help me? – George Jun 9 at 13:11
• $\sin(\mathrm{theta})=5/\mathrm{?}$. Now solve for ?. – Michael Hoppe Jun 9 at 14:27
• so 5/sin(theta) thank you – George Jun 9 at 14:38
• You're welcome. – Michael Hoppe Jun 9 at 14:39