Answer
See the steps.
Work Step by Step
Law of Cosines:
$$a^2 = b^2+c^2-2bc \cos{A} \\ \because A = 90 \hspace{15pt} \therefore \cos{A} = 0$$
$$\therefore a^2 = b^2+c^2$$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.