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x2=102+72 = 14
x= √149 = 12,2
and for b-c diagonal
y2=72+32=58
y= √58 = 7,616
and a-c
z2=12,22+7,6162=206,84
z = √206,84 = 14,3
so angle would be
cosθ=7,616÷14,38
θ = 58.19
