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Answer:
mCEA = 90ᴼ because CEA is a right angle, and right angles have 90ᴼ measures.
CEF is a straight angle because there are two 90ᴼ angles (CEA and AEF) and therefore there is 180ᴼ in total. A straight line has a measure of 180ᴼ.
AEF is a right angle because if CEA is a right angle and CEF is a straight line, then AEF has to be a right angle.
The three statements that must be true are:
m∠CEA = 90°
∠CEF is a straight angle
∠AEF is a right angle.
Let's analyze each of the given options using the information given to us and determine whether they are true or not:
- Statement 1: m∠CEA = 90°
The small rectangular sign-shape included in the diagram is used to indicate that a right angle which is 90°.
Therefore, the statement, "m∠CEA = 90°" is TRUE.
- Statement 2: m∠CEF = m∠CEA + m∠BEF
This is FALSE.
m<CEF = m<CEA + AEF NOT m∠CEF = m∠CEA + m∠BEF.
- Statement 3: "m∠CEB = 2(m∠CEA)"
This is also FALSE because,
m<CEB is half of m<CEA since ray EB bisects <CEA.
- Statement 4: "∠CEF is a straight angle."
This is TRUE, because,
m<CEF = m<CEA + m<AEF = 180° (straight line angle = 180°)
- Statement 5: "∠AEF is a right angle."
This is also TRUE because,
m<AEF = 90°
A right angle = 90°
- Therefore, the statements that must be TRUE considering the information given to us are:
m∠CEA = 90°
∠CEF is a straight angle
∠AEF is a right angle.
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