Question

find a unknown length of the sides​

Answer 1

Answer:

$a = 3\sqrt{7}$

Step-by-step explanation:

Given

See attachment

Required

Determine (a)

To do this, we make use of Pythagoras theorem.

$12^2 = a^2 + 9^2$

$144 = a^2 + 81$

Collect like terms

$a^2 = 144 -81$

$a^2 = 63$

Take square roots

$a = \sqrt{63}$

Expand

$a = \sqrt{9*7}$

Split

$a = \sqrt{9}*\sqrt{7}$

$a = 3\sqrt{7}$