unit 5 geometry vocab

Right Triangle

A triangle with one 90° angle.

Hypotenuse

The longest side of a right triangle (opposite the right angle).

Leg

One of the shorter sides of a right triangle.

Pythagorean Theorem

a² + b² = c² for right triangles.

Pythagorean Triple

Three whole numbers that fit a² + b² = c² (like 3-4-5).

Pythagorean Theorem – Classifying Right

If a² + b² = c², the triangle is right.

Pythagorean Theorem – Classifying Acute

If a² + b² > c², the triangle is acute (all angles < 90°).

Pythagorean Theorem – Classifying Obtuse

If a² + b² < c², the triangle is obtuse (one angle > 90°).

45-45-90 Special Right

A right triangle with angles 45°, 45°, 90°; sides follow x : x : √2.

30-60-90 Special Right

A right triangle with angles 30°, 60°, 90°; sides follow x : x√3 : 2x

Sine (sin)

Opposite side / hypotenuse.

Cosine (cos)

Adjacent side / hypotenuse.

Tangent (tan)

Opposite side / adjacent side.

Inverse Sine (sin⁻¹)

Finds the angle when you know a sine ratio.

Inverse Cosine (cos⁻¹)

Finds the angle when you know a cosine ratio.

Inverse Tangent (tan⁻¹)

Finds the angle when you know a tangent ratio.