2)
sina+cosa=1.3
(sina+cosa)^2= 1.69
sin^2a+2sina*cosa+ cos^2a=1.69
2sina*cosa = 1.69-1
sina*cosa=0.69/2
b)(sina+cosa)^3=sin3a+cos3a+3sina+3cosa/2=2.197
sin3a+cos 3a+3(cosa+sina)= 4.394
sin3a+cos3a=4.394-3
sina+cos3a =1.394
2)
sina+cosa=1.3
(sina+cosa)^2= 1.69
sin^2a+2sina*cosa+ cos^2a=1.69
2sina*cosa = 1.69-1
sina*cosa=0.69/2
b)(sina+cosa)^3=sin3a+cos3a+3sina+3cosa/2=2.197
sin3a+cos 3a+3(cosa+sina)= 4.394
sin3a+cos3a=4.394-3
sina+cos3a =1.394