Question Number 189793 by normans last updated on 21/Mar/23
Commented by mr W last updated on 22/Mar/23
Answered by HeferH last updated on 21/Mar/23
$$\mathrm{180}°\: \\ $$
Answered by HeferH last updated on 22/Mar/23
$$\mathrm{external}\:\mathrm{angle}\:\mathrm{1}:\:\angle\mathrm{A}\:+\angle\mathrm{C} \\ $$$$\mathrm{external}\:\mathrm{angle}\:\mathrm{2}:\:\angle\mathrm{B}\:+\:\angle\mathrm{D} \\ $$$$\mathrm{but}\:\mathrm{they}\:\mathrm{are}\:\mathrm{also}\:\mathrm{internal}\:\mathrm{for}\:\mathrm{the}\:\mathrm{triangle}\:\mathrm{with} \\ $$$$\mathrm{angle}\:\angle\mathrm{E} \\ $$$$\mathrm{now}:\:\angle\mathrm{A}\:+\:\angle\mathrm{B}+\angle\mathrm{C}+\angle\mathrm{D}+\angle\mathrm{E}\:=\:\mathrm{180}° \\ $$