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Junior one math line segment
C is a point on the straight line AB, D is the midpoint of the line segment AC, and E is the midpoint of the line segment CB. Given AB = 9 and AC = 5, please find the length of (1)AD and the length of (2)DE.

Solution: As shown in the figure.

D is the midpoint of the line segment AC,

Gets the length of the advertisement segment.

AD = DC = 1/2 AC = 5×( 1/2)= 2.5cm

identical

E is the midpoint of line segment CB,

Get the length of the line segment.

BE = CE = 1/2 BC = 4×( 1/2)= 2cm

∴ the length of line segment DE

DE=AB-AD-BE=9-2.5-2=4.5cm

Angle AOD and angle BOC are right angles. Given angle DOC=62, find the degree of angle AOB!

Solution:

There are two situations.

The first situation is as shown above.

∠∠BOD =∠BOC-∠DOC = 90-62 = 28,

∴? Angle AOB = ∠ AOD-∠ BOD = 90-28 = 62;

The second kind? The following figure

∠∠AOD+∠DOC+∠COB+∠AOB = 360,

Namely 90+62+90+∠ AOB = 360.

242 +∠AOB=360

∴? Angle AOB = 360-242 = 1 18.