Question

Find a unknown length of the sides​

Answer 1

`a = 3√(7)`

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 = √(63)`

Expand

`a = √(9*7)`

Split

`a = √(9)*√(7)`

`a = 3√(7)`