1-calculate-A-cos-pi-7-cos-2pi-7-cos-3pi-7-2-calculate-B-tan-pi-7-tan-2pi-7-tan-3pi-7-

Question Number 39028 by maxmathsup by imad last updated on 01/Jul/18

1) c a l c u l a t e A = c o s (\frac{π}{7}) . c o s (\frac{2 π}{7}) . c o s (\frac{3 π}{7})

2) c a l c u l a t e B = t a n (\frac{π}{7}) . t a n (\frac{2 π}{7}) . t a n (\frac{3 π}{7}) .

Answered by tanmay.chaudhury50@gmail.com last updated on 02/Jul/18

A \times 2 s i n \frac{Π}{7} = 2 s i n \frac{Π}{7} c o s \frac{Π}{7} c o s \frac{2 Π}{7} c o s \frac{3 Π}{7}

A \times 2 s i n \frac{Π}{7} = s i n \frac{2 Π}{7} c o s \frac{2 Π}{7} c o s \frac{3 Π}{7}

A \times 2^{2} s i n \frac{Π}{7} = s i n \frac{4 Π}{7} c o s \frac{3 Π}{7}

A \times 2^{3} s i n \frac{Π}{7} = 2 s i n \frac{4 Π}{7} c o s \frac{3 Π}{7}

A \times 2^{3} s i n \frac{Π}{7} = s i n Π + s i n \frac{Π}{7}

A \times 2^{3} s i n \frac{Π}{7} = s i n \frac{Π}{7}

A = \frac{1}{8}