18.Agar (bn) geometrik progressiyada b3 =12 va b5=48 bo’lsa, uning dastlabki oltita hadining yig’indisini toping.
19.Agar (bn) geometrik progressiyada b5= , q=. bo’lsa , uning dastlabki yettita hadining yig’indisini toping.
20.(bn ) goemetrik progressiyada b1=0,5; q=2; sn=31,5.
bo’lsa , n va bn ni toping
21. bn …; cheksiz kamayuvchi geometrik progressiyaning yig’indisini toping.
22.Cheksiz kamayuvchi geometrik progressiyaning yig’indisini toping, bunda
1+sin 30˚+sin² 30˚+sin³ 30˚+… .
23. Agar tgα = 2 va 0 < α
24.Ifodani soddalashtiring va sin α = da qiymatini toping:
25.cos ning qiymatini toping.
26.Ayniyatini isbotlang: (ctgα-tgα) sin 2α = 2cos 2α.
27.α va β lar II chorak burchaklari va sin α = , cos
β=. ekani ma’lum bo’lsa, cos (α+β) ni toping.
28.sin 20˚+sin 40˚-cos 10˚=0 ekanligini isbotlang.
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