Let’s solve this step by step.
We have a right triangle ABC, with the right angle at C. That means angle C is 90°. We’re told that angle A is 30°, and side AB (the hypotenuse) is 12 cm. We need to find the length of side BC — which is opposite the 30° angle.
In a right triangle, when you have a 30° angle, there’s a special rule:
→ The side opposite the 30° angle is
half the length of the hypotenuse.
Why? Because in a 30-60-90 triangle, the sides are always in the ratio:
1 : √3 : 2
where:
- 1 = side opposite 30°
- √3 = side opposite 60°
- 2 = hypotenuse
So if the hypotenuse is 12 cm, then the side opposite 30° (which is BC) must be half of that.
Let’s calculate:
BC = 12 ÷ 2 = 6 cm
Double-checking:
Angle A = 30° → opposite side is BC
Hypotenuse AB = 12 cm
Yes — so BC = 6 cm makes sense.
Final Answer:
6 cm
Parent Tip: Review the logic above to help your child master the concept of sin cos tan practice worksheet.
