Вычислите cos(arccos 5/13+arcsin 7/25)

cos(arccos 5/13+arcsin 7/25)=(5/13+√(625/625-49/625))=5/13+24/25=437/325

Cos(x)=0                                       cos(π/6 +x)=0 x=π/2 +πn; n∈z                             π/6 +x=π/2 +πn; n∈z                                                      x=π\3 +πn; n∈z

Б)2(а-1)^2 + 3(а-2)^2= 2(a^2 - 2a + 1) +3(a^2 - 4a + 4)= 2a^2-4a+2+3a^2-12a+12=  5a^2 + 8a +14 г)4(m-2n)^2-3(3m+n)^2 = 4(m^2 - 4mn + 4n^2) - 3(9m^2  +  6mn  + n^2) = 4m^2 - 16mn + 16n^2 - 27m^2 - 18mn - 3n^2 = -23m^2 - 34mn + 13n^2 е)4(3x + 4y)^2 - 7(2x - 3y)^2 = 4(9x^2 +  24xy + 16y^2) - 7(4x^2 - 12xy + 9y^2) = 36x^2 + 96xy + 64y^2 -  28x^2 + 84xy - 63y^2 = 8x^2 + 180xy + y^2 з)5(n^2 - 10mn + 25m^2) - 6(4n^2 -12mn + 9m^2) - (21m^2 - 3mn - 7mn +n^2) = 5n^2 - 50mn +125m^2 - 24n^2 + 72mn -  54m^2 -21m^2 + 10mn - n^2 = -20n^2 32mn + 50m^2