(1+cospi/9) * (1+cos3pi/9) *(1+cos5pi/9) * (1+cos7pi/9) the value of this expression Share with your friends Share 0 Anuradha Sharma answered this Dear Student, We know that π9= 20 degreeSo our equation will be, 1+cos201+cos601+cos1001+cos140= 1+cos201+121+cos1001+cos140=321+cos201+cos120-201+cos140+20= 321+cos201+cos120cos20+sin120sin201+cos120cos20-sin120sin20= 321+cos201+-12×cos20+32sin201+-12×cos20+32sin20= 321+cos201+-12×cos20+32sin201+-12×cos20-32sin20=321+cos201-12×cos202-34sin220= 321+cos201+cos2204-cos20-34sin220But here you have to put the value pof cos20.Regards -5 View Full Answer
