Question

find the exact value of sin a in simplest radical form.

Explanation:

Step1: Recall sine definition

In a right triangle, $\sin\theta = \frac{\text{opposite}}{\text{hypotenuse}}$. For $\angle A$, the opposite side is $BC = 21$, hypotenuse is $AB = 29$.

Step2: Apply the formula

$\sin A = \frac{BC}{AB} = \frac{21}{29}$ (already in simplest form as 21 and 29 are coprime).

Answer:

$\frac{21}{29}$