Question 1189695
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I'm not sure why you mentioned triangle ABC, but I'll ignore that portion. 


Drawing:
<img src = "https://i.imgur.com/Gtq9Kdb.png">
The diagram isn't to scale


Use the pythagorean theorem to find the missing side m
m^2 + n^2 = o^2
m^2 + 5^2 = (5.7)^2
m^2 + 25 = 32.49
m^2 = 32.49 - 25
m^2 = 7.49
m = sqrt(7.49)
m = 2.736786
That value is approximate


Now use the tangent ratio to help find angle M
tan(angle) = opposite/adjacent
tan(M) = m/n
tan(M) = 2.736786/5
M = arctan(2.736786/5)
M = 28.6944097
That value is approximate


Do the same idea for angle N
tan(angle) = opposite/adjacent
tan(N) = n/m
tan(N) = 5/2.736786
N = arctan(5/2.736786)
N = 61.3055903
That value is approximate


Or notice that
M+N = 90
N = 90-M
N = 90-28.6944097
N = 61.3055903



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Summary:


Side lengths:
<font color=red>m = 2.736786</font> (approximate)
<font color=black>n = 5</font> 
<font color=black>o = 5.7</font>


Angles
<font color=red>M = 28.6944097 degrees</font> (approximate)
<font color=red>N = 61.3055903 degrees</font> (approximate)
<font color=black>O = 90 degrees</font>
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