1) Упростим выражение:

(sinA+cosA)^2 - 1 - 2tgA - sinA*cosA

(sinA+cosA)^2 - 1 - 2(sinA/cosA) - sinAcosA
(sinA+cosA)^2 - 1 - 2sinA - sinAcosA
(sinA^2 + 2sinAcosA + cosA^2) - 1 - 2sinA - sinAcosA
1 + 2sinAcosA - 1 - 2sinA - sinAcosA
sinAcosA - 2sinA - sinAcosA
-2sinA

sin^2(π+A) = sin^2(π)sin^2(A) - 2sin(π)sin(A)cos(A) + cos^2(A)
= 0 - 201 + 1
= 1
sin^2(π+A) = 1

2) Найдем значение выражения:

sin(7A)cos(3A) - cos(7A)sin(3A)

A = π/16

sin(7A) = sin(7π/16) = sin(7π/16)
cos(3A) = cos(3π/16) = cos(3π/16)
cos(7A) = cos(7π/16) = cos(7π/16)
sin(3A) = sin(3π/16) = sin(3π/16)

sin(7π/16)cos(3π/16) - cos(7π/16)sin(3π/16)
sin((7π/16) + (3π/16))
sin(10π/16)
sin(5π/8)