.

M is the midpoint of 0A. N is the midpoint of OB. Prove that AB is parallel to MN​

Construct MN.

Since M is the midpoint of OA, OM = MA

Similarly, N is the midpoint of OB.

Thus, ON = NB.

Now, in Δs OMN and OAB,

∠MON = ∠AOB (common angle)

(sides are in proportional ratio; OA = 2OM and OB = 2ON)

∴ Δs OMN and OAB are similar (2 sides are in proportion, with the included angle)

Since they are similar, then ∠OMN = ∠OAB (corresponding angles of similar triangles are equal)

But since ∠OMN = ∠OAB, then that means MN || AB (corresponding angles of two lines must be equal since they also sit relative to the transverse line, OA)

Thus, AB || MN (QED)

40 is the final : )

127

whether it's diameter, or radius, i believe if i remember correctly from school, every amount has to always add up to 180. so if you take 53, and starting adding, long story short, taking 127 and adding it to 53, gives you 180.