[4f_(4)=cos(pi)/(4)+i sin(pi)/(6),pi a|z|bar(sigma)| pi|_(7)!=-],[[" (a) "1," (b) "(1)/(2)],[" (c) "(sqrt(3))/(2)," (d) "quad (1)/(5+4)vec 7-(1)/(4)| xi-(pi)/(78)]]

If z=cos((pi)/(4))+i sin((pi)/(6)), then

cos(pi/4-A)-sin(pi/4+A)=0

If z = cos (pi)/(4) + i sin (pi)/(6) , then

If z = cos"" pi/4+ isin (pi/6) ,then

z = (1+cos6 pi)+i sin6 pi

Prove that (i) "sin " (7pi)/(12) " cos " (pi)/(2) - "cos " *(7pi)/(12) " sin " (pi)/(4) = (sqrt(3))/(2) (ii) " sin " (pi)/(4) " cos " (pi)/(2) + "cos"(pi)/(4) " sin " (pi)/(12) = (sqrt(3))/(2) (iii) " cos " (2pi)/(3) " cos " (pi)/(4) - " sin " (2pi)/(3) " sin " (pi)/(4) =(-(sqrt(3) +1))/(2sqrt(2))

sin (pi/2) = 2 sin(pi/4) cos (pi/4)

"cos"(2pi)/(7) +"cos"(4pi)/(7)+"cos"(6pi)/(7)

cos.(2pi)/(7)+cos.(4pi)/(7)+cos.(6pi)/(7)

cos.(2pi)/(7)+cos.(4pi)/(7)+cos.(6pi)/(7)