In a right triangle, which side is called the hypotenuse?

Class 10Introduction to TrigonometryTrigonometry

AThe side opposite the right angle
BThe side adjacent to the chosen acute angle
CThe shortest side
DAny of the two legs

Step-by-Step Solution

The hypotenuse is always the side opposite the 90° angle and is the longest side of a right triangle.

Answer: A) The side opposite the right angle

Key idea: Why ratios — and not lengths

Two right triangles with the same acute angle θ are SIMILAR (Class 10 ch. 6 — AA criterion: both have a right angle and the angle θ).

Similar triangles → corresponding sides in fixed ratio.
So the ratio (opposite / hypotenuse) takes the SAME value in any right triangle with angle θ — regardless of how big the triangle is.

That's why sin θ, cos θ, tan θ are FUNCTIONS of the angle alone — they're well-defined.

This is the fundamental reason trigonometry works as a clean theory.

Master this chapter in 30 minutes a day.

Don't just memorise the answer — build a daily practice habit.

Practice 5 Similar Questions Free →

All Introduction to Trigonometry practice questions

More Class 10 Introduction to Trigonometry practice

Evaluate: 5 cos²60° + 4 sec²30° − tan²45°. (Give the exact value.)Assertion (A): sin 60° = √32. Reason (R): In an equilateral triangle of side 2, the…Simplify: cos 38° · cos 52° − sin 38° · sin 52°. (Hint: 38° and 52° are complementary.)If sin A = 1/2, what is the value of 3 cos A − 4 cos³A? (A is acute.)The maximum value that sin θ can take is: