# Determine the angle M in ΔMNO with side measures 0.8 m = n, o = 60 cmand m=100 cm

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In triangle MNO ,

o=60cm

m=100 cm

n=.8 x m=8 x 100 =80cm

By cos angle formula

`m^2=n^2+o^2-2nocos(M)`

`cos(M)=(m^2-n^2-o^2)/(2xxnxxo)`

`=(100^2-80^2-60^2)/(2xx60xx80)`

`=0`

Thus

M is right angle

`/_M=pi/2`