Mathematics for IGCSE & O level - Angles (Section 3 - No. 42)
In a triangle with angles x, 2x, and 3x, what kind of triangle is it?
Acute
Obtuse
Right
Equilateral
Giải thích
x+2x+3x=180, 6x=180, x=30, then 3x=90, this means one angle is 90, that is a right angle.