Răspuns:
Explicație pas cu pas:
Avem R=((r2-1)^2+1^2)^0.5 =A
sin2a = (r2-1)/A
cos 2a = 1/A
sin 4a= 2*(r2-1)/A^2
cos 4a = 1/A2- (r2-1)^2/A2=2*(r2-1)/A2
tg 4a = sin 4a/cos 4a= 1
b) R=(2^2+3^2)^0.5=r13
sin x/2= -2/r13
cos x/2= 3/r13
sin x=-12/13
cos x= 5/13
(2+3cos x)/(4-5sinx)= (2+3*5/13)/(4+5*12/13)= 41/112
c) R= (p2+q2)^0.5=A
sin a = p/A
cos a = q/A
sin 2a = 2pq/A2
cos 2a= (q2-p2)/A2
p*2pq/A2+q*(q2-p2)/A2=(2p2q+q3-p2q)/A2=(p2q+q3)(p2+q2)
