Curriculum placement
Geometry. This describes the skill, not a learner estimate.
Side ratios of special right triangles
Derive and use special right-triangle side ratios
Problem types
- Isosceles right triangle lengths as decimals
- 45-45-90 and 30-60-90 triangles
- Special triangles inside other figures
- Side of a similar isosceles right triangle with a radical
Builds on
- Sine, cosine, and tangent
- Distance in the coordinate plane · Useful idea
The distance from (0, 0) to (1, 1) is the square root of 2, which is the hypotenuse of a 45-45-90 triangle.
Leads to
- Radians and the unit circle
- Exact values at special angles
- The complex plane · See it applied
The point 1 + i forms a 45-45-90 triangle with the axes, so its modulus is the square root of 2 and its angle is 45 degrees.
Related skills
- Sine and cosine of complementary angles · Shared foundations
- The laws of sines and cosines · Shared foundations
- Area from two sides and the included angle · Shared foundations
- Vectors and their components · Shared foundations
Open the interactive map to explore lessons and skill connections.