In this lesson students deepen their understanding of trigonometry by completing an Information Gap. During this routine, students will reinforce the idea that trigonometry is based on right triangles. So far students have encountered trigonometry only with triangles in which an angle is given. At this point, students need one side length and one acute angle measure to calculate the remaining side lengths and angle measures.

Students then have the opportunity to apply this knowledge to some indirect measurement problems. During the discussion they consider rounding errors again, this time by comparing the estimation to an exact value. The effect of rounding is much more pronounced with large numbers, so this discussion may convince students who were skeptical in previous lessons.

During the Information Gap activity, students work to refine the language they use and ask increasingly more precise questions until they get the information they need (MP6).