50 o
Explanation:
The sum of the measure of the internal angles of any triangle is
180 o .
In a right angled triangle, one angle will be 90 o .
Since we know the measure of one of the other acute (less than 90 o ) angles, we subtract the sum of the two known angles from 180 to calculate the measure of the other acute angle.
180 − ( 90 + 40 )
180 − 130
50