Răspuns:
Explicație pas cu pas:
Ex10
a) ∡A=90°, ⇒∡B+∡C=90° ⇒x-10+x+10=90° ⇒2x=90° ⇒x=45°. Atunci ∡B=45°-10°=35°, iar ∡C=45°+10°=55°.
b) ∡A+∡B+∡C=180° ⇒2x+5+40+x=180 ⇒3x=135, ⇒x=135:3=45
Atunci ∠A=2·45+5=95°, ∡C=45°.
c) 4x+12+70+5x-10=180 ⇒9x=108 ⇒x=108/9=12°. Atunci ∡A=4·12+12=50°, ∡C=5·12-10=50°
Ex13
a) In ΔABD, ∡ABD=180°-(∡B+∡D)=180°-82°=98°.
∡BAC=180°-115°=65°. ⇒∡CAD=∡ABD-∡BAC=98°-65°=33°.
b) ∡CBD=180°-(42+38)=100°
∡BDA=180°-(42+62)=76°. Dar ∡CBD=∡BDA+∡A, ⇒100°=76°+∡A, deci ∡A=24°=∡CAD.