The value of sin 30° is:
A1/2
B√3/2
C1
D0
Answer & Solution
Correct answer: A. 1/2
To find the value of $\sin 30^\circ$, we can use the properties of a special right-angled triangle: the $30^\circ-60^\circ-90^\circ$ triangle.
### 1. The Geometry Approach
Consider an equilateral triangle with side length $2$. If we draw an altitude from one vertex to the opposite side, we split it into two congruent right-angled triangles with angles $30^\circ$, $60^\circ$, and $90^\circ$.
- The **Hypotenuse** of this triangle is $2$.
- The **Base** (side opposite $30^\circ$) is half the original side, which is $1$.
- The **Altitude** (side opposite $60^\circ$) can be found using the Pythagorean theorem: $1^2 + h^2 = 2^2 \implies h = \sqrt{3}$.
### 2. Definition of Sine
The sine of an angle is defined as the ratio of the length of the opposite side to the length of the hypotenuse:
$$\sin(\theta) = \frac{\text{Opposite}}{\text{Hypotenuse}}$$
### 3. Calculation
For $\theta = 30^\circ$:
- Opposite side = $1$
- Hypotenuse = $2$
Substituting these values:
$$\sin 30^\circ = \frac{1}{2}$$
Thus, the value of $\sin 30^\circ$ is $1/2$ or $0.5$.
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