5,

a,

`gamma` = 180-105 = 75°

`alpha` = `180-(gamma+45)` = 180-(75+45) = 60°

b,

`beta` = 90-45 = 45°

c,

`alpha` = 180-130 = 50°

`beta` = 180-130 = 50°

6,

a,

`gamma` = `180-(alpha+beta)` = `180-(38+62)` = 80°

Sorrend: c, b, a.

b,

`beta` = `180-beta'` = 180-72 = 108°

`gamma` = `180-(alpha+beta)` = 180-(68+108) = 4°

sorrend: b, a, c

c,

`alpha` = `180-alpha'` = 180-145 = 35°

`beta` = `180-beta'` = 180-63 = 117°

`gamma` = `180-(alpha+beta)` = 180-(35+117) = 28°

Sorrend: b, a, c

7,

a,

`2*alpha+beta` = `2*30+120` = 180°; egyenlőszárú.

b,

`beta` = `180-beta'` = 180-120 = 60°

`alpha+2*beta` = `35+2*60` = 155° `ne` 180°

`2*alpha+beta` = `2*35+60` = 130° `ne` 180°

A háromszög nem egyenlőszárú.

c,

`alpha` = 60°

`beta` = `180-beta'` = 180-120 = 60° = `alpha`

A háromszög egyenlőszárú.