Question Number 133242 by Kunal12588 last updated on 20/Feb/21
Commented by Kunal12588 last updated on 20/Feb/21
$$\mathrm{book}\:\mathrm{says}\:\mathrm{it}\:\mathrm{is}\:\mathrm{easy}\:\mathrm{to}\:\mathrm{show}\:\mathrm{after}\:\mathrm{that} \\ $$$$\mathrm{but}\:\mathrm{how}?\:\mathrm{also}\:\mathrm{then}\:\mathrm{we}\:\mathrm{can}\:\mathrm{prove}\:\bigtriangleup\mathrm{ADB} \\ $$$$\mathrm{is}\:\mathrm{a}\:\mathrm{36}°-\mathrm{72}°-\mathrm{72}°\:\mathrm{triangle} \\ $$