POST-ASSESSMENT
Direction: Complete the proof by writing reason for each statement
EXTERIOR ANGLE INEQUALITY THEOREM
The measure of an exterior angle of a triangle is greater than the measure of either remote
interior angle
Given: ALMN with exterior angle ZLNP
Prove: m_LNP > MMLN
M
N P
PROOF:
LET US PROVE THAT MZLNP > MZMLN BY CONSTRUCTING THE FOLLOWING:
1. MIDPOINT Q ON LN SUCH THAT LQ=NQ
2. MR THROUGH Q SUCH THAT MQ = QR
R
3
1
2
M
N
Р
REASONS
STATEMENTS
1. LQ = NQ; MQ = QR
2. 23 24
1. BY CONSTRUCTION
2.
3. ALQM = ANQR
3
3.
4. ZMLN = 21
4.
5. ZLNP: 21+ 22
6. LLNP> 21
7. ZLNP>LMLN
5.
6. PROPERTY OF INEQUALITY
7.
6
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