CCSS.Math.Content.HSG-SRT.C.8
The standard
Use trigonometric ratios and the Pythagorean Theorem to solve right triangles in applied problems.
Common Core State Standards for Mathematics
What this standard means
Students need to choose sine, cosine, tangent, or the Pythagorean Theorem to find missing side lengths and angles in right triangle situations. They must read a context, sketch or label the triangle, identify the known parts, and set up an equation that matches the question.
Mastery looks like picking the right tool without guessing, using inverse trig correctly, keeping units, and giving an answer that makes sense in the context. Students often mix up opposite and adjacent, use degrees or radians incorrectly, round too early, or forget that the longest side is the hypotenuse.
Ways to teach it
- Have students use tape on the floor to build a right triangle, measure two sides, then calculate the missing side and angles.
- Ask students to explain which ratio they would use for a ladder against a wall problem, and why not the other two.
- Give a one problem exit ticket with a labeled diagram, asking for one missing side and one missing angle.
- Use a smartphone clinometer app to estimate the height of a flagpole, tree, or gym wall from a measured distance.
Plan a lesson for CCSS.Math.Content.HSG-SRT.C.8
Generate a complete lesson plan aligned to this standard, with objectives, activities, and materials. Free, no account needed.
Related standards
- CCSS.Math.Content.8.G.B
Understand and apply the Pythagorean Theorem.
- CCSS.Math.Content.HSG-SRT.C
Define trigonometric ratios and solve problems involving right triangles
- CCSS.Math.Content.HSG-SRT.D
Apply trigonometry to general triangles
- CCSS.Math.Content.8.G.B.7
Apply the Pythagorean Theorem to determine unknown side lengths in right triangles in real-world and mathematical problems in two and three dimensions.