CCSS.Math.Content.HSG-SRT.C
The standard
Define trigonometric ratios and solve problems involving right triangles
Common Core State Standards for Mathematics · High School — Geometry
What this standard means
Students need to connect right triangle side relationships to sine, cosine, and tangent. They should choose the correct ratio, set up an equation, and solve for a missing side length or angle. They also need to use a calculator correctly for trig values and inverse trig.
Mastery looks like labeling opposite, adjacent, and hypotenuse from the chosen angle, not from the picture’s orientation. Students can explain why a ratio fits the problem and check if an answer is reasonable. Common trouble spots are mixing up sine and cosine, using degrees or radians incorrectly, and forgetting that inverse trig finds an angle, not a side.
Ways to teach it
- Have students measure classroom ramp height and length with tape measures, then calculate the ramp angle using inverse sine.
- Ask students to write: How do you decide between sine, cosine, and tangent when one angle is marked?
- Give a three-question exit ticket: find one missing side, one missing angle, and identify the needed trig ratio only.
- Show a ladder against a wall photo, give two measurements, and ask students to find the safe ladder angle.
Plan a lesson for CCSS.Math.Content.HSG-SRT.C
Generate a complete lesson plan aligned to this standard, with objectives, activities, and materials. Free, no account needed.
Related standards
- CCSS.Math.Content.HSG-SRT.C.6
Understand that by similarity, side ratios in right triangles are properties of the angles in the triangle, leading to definitions of trigonometric ratios for a...
- CCSS.Math.Content.HSG-SRT.D
Apply trigonometry to general triangles
- CCSS.Math.Content.HSF-TF.C
Prove and apply trigonometric identities
- CCSS.Math.Content.HSG-SRT.C.8
Use trigonometric ratios and the Pythagorean Theorem to solve right triangles in applied problems.