ANSWER
a = √21
Step-by-step explanation
This is a right triangle, so we have to apply the Pythagorean Theorem to find the value of a.
We know the length of the hypotenuse which is 5, and the length of one of the legs, which is 2. The Pythagorean Theorem for this problem is,
Subtract 2² from both sides,
And take the square root to both sides,
Hence, the value of a is √21.