鈍角(どんかく)

鈍角(どんかく) is a mathematical term for an obtuse angle (between 90° and 180°).

KANJI BREAKDOWN:
鈍(どん) (dull, blunt) + 角(かく) (angle, corner)

ANGLE CLASSIFICATION:

• 鋭角(えいかく): acute angle (0° < θ < 90°)
• 直角(ちょっかく): right angle (θ = 90°)
• 鈍角(どんかく): obtuse angle (90° < θ < 180°)
• 平角(へいかく): straight angle (θ = 180°)

TRIANGLE TYPES BY ANGLE:

• 鋭角(えいかく)三角形(さんかくけい): acute triangle
• 直角(ちょっかく)三角形(さんかくけい): right triangle
• 鈍角(どんかく)三角形(さんかくけい): obtuse triangle

RELATED MATH TERMS:
角度(かくど) (angle measurement), 度(ど) (degree)