a/b + b/a = (a² + b²)/(ab) = (sin² x + 1 + cos² x + 2 cos x) / sin x (1 + cos x) = 2(1 + cos x) / sin x (1 + cos x) = 2/sin x TerBukTi
▶ csc (180° + A) . csc (180° - A) - tan (90° + A) . cot (180° + A) = -csc A . csc A - (-cot A) . tan A = -csc² A + 1 = 1 - csc² A = (sin² A - 1)/sin² A = -cos² A /sin² A = -cot A
Verified answer
▶Misal :
a = sin x
b = 1 + cos x
a/b + b/a
= (a² + b²)/(ab)
= (sin² x + 1 + cos² x + 2 cos x) / sin x (1 + cos x)
= 2(1 + cos x) / sin x (1 + cos x)
= 2/sin x
TerBukTi
▶
csc (180° + A) . csc (180° - A) - tan (90° + A) . cot (180° + A)
= -csc A . csc A - (-cot A) . tan A
= -csc² A + 1
= 1 - csc² A
= (sin² A - 1)/sin² A
= -cos² A /sin² A
= -cot A