Answer:
The radius is 5 cm
Step-by-step explanation:
The formula for the area of a circle is : 
To work out the length of the radius you would first need to divide the area of 78.5 cm by pi (pi=3.14), this gives you
. This is because by dividing the area by pi we are isolating the value of the radius squared.
The final step is to work out the radius. You can do this by finding the square root of the radius squared which is 25, this gives you 5 cm. This means that the radius is 5 cm. This is because the square root is a number that when squared equals that number.
1) Divide 78.5 by pi.

2) Find the square root of 25 cm squared.

In this question pi is 3.14
Answer:
A construction worker may use trigonometry when building the roof of a house. They may have to calculate the right angle that hypotenuse must sit at so water doesn't build up on the roof and cause leaks.
(this may be more of an architect's job, as they are the ones that design the houses)
or
An air traffic controller may use trigonometry to find how long it will take an airplane to land/how far the airplane is from the ground while it is in the sky (hypotenuse), based on its height from the ground (opposite) and the distance away from the runway it is (adjacent). They can also calculate the angle of elevation of the airplane from the tower they work in.
The word will depend on how many equal shares there are. For example, if there are two equal shares, you can say "halves"; if there are three equal shares, you can say "thirds"; if there are four equal shares, you can say "quarters," etc.