Here are a few reasons: 
The triangles have the same three sides 
The triangles have the same three angles
The triangles could perfect overlap one another 
They have corresponding angles.
Not sure if this helped but I hope so! 
 
        
             
        
        
        
Step-by-step explanation:
cos θ = 3 / AB
When θ = 28°:
cos 28° = 3 / AB
AB = 3 / cos 28°
AB ≈ 3.4
When AB = 5.2:
cos θ = 3 / 5.2
θ = cos⁻¹(3 / 5.2)
θ ≈ 54.8°
 
        
             
        
        
        
Answer:  2, 2, 13, 13
Step-by-step explanation: Prime number are numbers that can divide without remainder, This means that 676 is divisible by 2, 2, 13, 13, numbers.
 
        
             
        
        
        
Answer:
   see below. The solution is the doubly-shaded area.
Step-by-step explanation:
Each boundary line will be dashed, because the "or equal to" case is <em>not included</em>. Each shaded area will be above the corresponding boundary line because the comparison symbol is y > .... That is, only y-values greater than (above) those in the boundary line are part of the solution.
Of course, the boundary lines are graphed in the usual way. Each crosses the y-axis at the value of the constant in its equation. Each has a slope (rise/run) that is the value of the x-coefficient in the equation.
 
        
                    
             
        
        
        
Answer:
x=90º
Step-by-step explanation:
x=60+30
x=90