Transitive Property of Equality Variation 2
Sides of an Equilateral Triangle
Sides of an Equilateral Triangle 2
Distance Property 1
Angle Symmetry Example 2
Collinear Angles Property 9
Transitive Property Application 2
Angles of an Isosceles Triangle
Angles of an Isosceles Triangle 5
Angles of an Equilateral Triangle
Distance Property 2
Transitive Property of Equality Variation 3
Angle Symmetry Property 5
Angles of an Isosceles Triangle 4
Angles of an Isosceles Triangle 4 A
Angles of an Equilateral Triangle 2
Angles of an Equilateral Triangle 3
Transitive Property of Equality Variation 1
Propagated Transitive Property 3
Angles of an Equilateral Triangle 4
Collinear Then 180
Subtract Both Sides
Add Term to Both Sides 6
Subtract Both Sides 2
Add Term to Both Sides 7
Vertical Angles
Angle Addition Theorem
Collinear Angles B
Exterior Angle
Exterior Angle B
Collinear Angles Property 10
Collinear Angles Property 3
Collinear Angles Property 3 B
Collinear Angles Property 3 C
alternate interior angles then parallel
ParallelThenAIA
Parallelthenaiashort
Commutative Property Example 2
Commutative Property Variation 1
Substitution 2
Substitution 8
Angle Symmetry B
Substitution Example 10
Substitute First Term
Triangles Sum to 180
Substitute 2
Add Term to Both Sides 2
Multiplicative Identity 2
Distributive Property 4
Multiplicative Property of Equality Variation 1
Addition Theorem
Add Three
Divide Both Sides
Multiplicative Property of Equality Variation 2
Division is Commutative
Associative Property
Divide Each Side
Equilateral Triangle 60
Angles of an Equilateral Triangle 5
Angles of an Equilateral Triangle 6
Equilateral Triangle 60 2

Proof: Collinear Angles Property 10

Let's prove the following theorem:

if m∠ABC = 180, then m∠XCB = m∠XCA

C A B X

Proof:

View as a tree | View dependent proofs | Try proving it

Given
1 m∠ABC = 180
Proof Table
# Claim Reason
1 m∠BCX = m∠ACX if m∠ABC = 180, then m∠BCX = m∠ACX
2 m∠BCX = m∠XCB m∠BCX = m∠XCB
3 m∠ACX = m∠XCA m∠ACX = m∠XCA
4 m∠XCB = m∠ACX if m∠BCX = m∠XCB and m∠BCX = m∠ACX, then m∠XCB = m∠ACX
5 m∠XCB = m∠XCA if m∠XCB = m∠ACX and m∠ACX = m∠XCA, then m∠XCB = m∠XCA
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