Answer:
   about 1.56637 radians ≈ 89.746°
Step-by-step explanation:
The reference angle in radians can be found by the formula ...
   ref angle = min(mod(θ, π), π -mod(θ, π))
Equivalently, it is ...
   ref angle = min(ceiling(θ/π) -θ/π, θ/π -floor(θ/π))×π 
<h3>Application</h3>
When we divide 11 radians by π, the result is about 3.501409. The fractional part of this quotient is more than 1/2, so the reference angle will be ...
   ref angle = (1 -0.501409)π radians ≈ 1.56637 radians ≈ 89.746°
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<em>Additional comment</em>
For calculations such as this, you need to use the most accurate value of pi available. The approximations 22/7 or 3.14 are not sufficiently accurate to give good results.
 
        
             
        
        
        
+1/31 and -1/31
Hope this helps.
        
             
        
        
        
Answer:
I take it you mean the average gallons lost an hour, in which case you would do 58,432.4 - 56,475.2 to get 1,597.2 to which you divide by 2 getting your final answer of 978.6