In a right triangle, according to the Pythagorean Theorem, the relationship between the lengths of the sides is given by the formula:
\[ a^2 + b^2 = c^2 \]
where \( c \) is the length of the hypotenuse (the side opposite the right angle), and \( a \) and \( b \) are the lengths of the other two sides.
In your case, the triangle is labeled as follows:
- \( m \) is the length of one leg,
- \( n \) is the length of the other leg, and
- \( o \) is the length of the hypotenuse.
Therefore, according to the Pythagorean Theorem, the relationship in this triangle is:
\[ m^2 + n^2 = o^2 \]
So the answer would be:
\[ m^2 + n^2 = o^2 \]