Answer:
19.9
Explanation:
As 21 is opposite the right angle this side must be the hypotenuse :
Pythagoras Theorem says :
a² + b² = c²
Where c is the hypotenuse.
Substituting values in gives us (a and b do not matter) :
x² + (√43)² = 21²
Now we simplify :
Using the surd law:
√a ×√a = a
(√43)² = √43×√43 = 43
21² = 441
x² + 43 = 441
Subtract 43 from both sides :
x² + 43 - 43 = 441 - 43
x² = 398
Square root both sides :
x = √398
√398 = 19.9 to 1 d.p.
Hope this helped and have a good day