Question

in circle j with $m\angle hlk = 21^\circ$, find the $m\angle hjk$.

Explanation:

Step1: Identify angle relationship

$\angle HLK$ is an inscribed angle, $\angle HJK$ is a central angle, both intercept arc $HK$. The central angle is twice the inscribed angle.

Step2: Calculate central angle

$\text{m}\angle HJK = 2 \times \text{m}\angle HLK$
$\text{m}\angle HJK = 2 \times 21^\circ$

Answer:

$42^\circ$