Answer:
a=4
Explanation:
Hi there!
We are looking for the value of 
 . We know that
. We know that 
 and
 and 
 .
.
We'll start with the Pythagorean theorem:

Now, we'll subtract 
 from both sides so that
 from both sides so that 
 is by itself.
 is by itself.

We can now substitute our known values of 
 and
 and 
 into the equation. Make sure to put the substituted values in parenthesis.
 into the equation. Make sure to put the substituted values in parenthesis.

Let's apply the exponents to the values we substituted in:


Now, to eliminate the exponent on 
 , we take the square root of both sides:
, we take the square root of both sides:


Let me know if you have any questions!