Baixe o app para aproveitar ainda mais
Prévia do material em texto
Tiago Lima - Instagram: @professor_disciplinas_exatas / WhatsAPP: (71) 9927-17449 • Demonstre as seguintes identidades trigonométricas: d) tan x - sen x + 1 - cos x = sec x - 1( ( ) ( ))2 ( ( ))2 ( ( ) )2 Resolução: Já sabemos que; tan x = e sec x =( ) sen x cos x ( ) ( ) ( ) 1 cos x( ) Substituindo e simplificando fica; tan x - sen x + 1-cos x = sec x -1 -sen x + 1-2cos x + cos x = -1( ( ) ( ))2 ( ( ))2 ( ( ) )2 → sen x cos x ( ) ( ) ( ) 2 ( ) 2( ) 1 cos x( ) 2 + 1-2cos x + cos x =→ sen x - cos x sen x cos x ( ) ( ) ( ) ( ) 2 ( ) 2( ) 1-cos x cos x ( ) ( ) 2 + 1-2cos x + cos x =→ sen x - cos x sen x cos x ( ( ) ( ) ( ))2 2( ) ( ) 2( ) 1-cos x cos x ( ( ))2 2( ) = 1-2cos x + cos x→ sen x -2sen x cos x sen x + cos x sen x + cos x -2cos x + cos x cos x 2( ) ( ) ( ) ( ) 2( ) 2( ) 2( ) 3( ) 4( ) 2( ) 1 cos x2( ) ( ) 2( ) sen x -2cos x sen x + cos x sen x + cos x -2cos x + cos x = 1-2cos x + cos x→ 2( ) ( ) 2( ) 2( ) 2( ) 2( ) 3( ) 4( ) cos x cos x 2( ) 2( ) ( ) 2( ) sen x -2cos x 1-cos x + cos x 1-cos x + cos x -2cos x + cos x = 1 ⋅ 1-2cos x + cos x→ 2( ) ( ) 2( ) 2( ) 2( ) 2( ) 3( ) 4( ) ( ) 2( ) sen x -2cos x + 2cos x + cos x - cos x + cos x -2cos x + cos x = 1-2cos x + cos x→ 2( ) ( ) 3( ) 2( ) 4( ) 2( ) 3( ) 4( ) ( ) 2( ) sen x -2cos x + 2cos x + 2cos x - cos x = 1→ 2( ) ( ) 2( ) ( ) 2( ) sen x + cos x = 1→ 2( ) 2( ) (verdadeiro ) e) cossec x ⋅ tan x = cotg x ⋅ sec x2( ) ( ) ( ) 2( ) Resolução: Sabemos que; tan x = , cossec x = e cotg x =( ) sen x cos x ( ) ( ) ( ) 1 sen x( ) ( ) cos x sen x ( ) ( ) Substituindo e simplificando fica; cossec x ⋅ tan x = cotg x ⋅ = ⋅2( ) ( ) ( ) → 1 sen x( ) 2 sen x cos x ( ) ( ) cos x sen x ( ) ( ) 1 cos x( ) 2 ⋅ = ⋅ ⋅ = ⋅→ 1 sen x2( ) sen x cos x ( ) ( ) cos x sen x ( ) ( ) 1 cos x2( ) → sen x sen x ( ) 2( ) 1 cos x2( ) cos x sen x ( ) ( ) 1 cos x2( ) ⋅ = ⋅→ 1 sen x( ) 1 cos x( ) 1 sen x( ) cos x cos x ( ) 2( ) ⋅ = ⋅ 1 sen x( ) 1 cos x( ) 1 sen x( ) 1 cos x( ) f) sec x ⋅ cossec x = sec x + cossec x2( ) 2( ) 2( ) 2( ) Resolução: Já sabemos que; sec x = e cossec x =( ) 1 cos x( ) ( ) 1 sen x( ) Substituindo e simplificando fica; sec x ⋅ cossec x = sec x + cossec x ⋅ = +2( ) 2( ) 2( ) 2( ) → 1 cos x( ) 2 1 sen x( ) 2 1 cos x( ) 2 1 sen x( ) 2 ⋅ = + =→ 1 cos x2( ) 1 sen x2( ) 1 cos x2( ) 1 sen x2( ) → 1 cos x sen x2( ) 2( ) sen x + cos x cos x sen x 2( ) 2( ) 2( ) 2( ) = sen x + cos x =→ sen x + cos x cos x sen x 2( ) 2( ) 2( ) 2( ) 1 cos x sen x2( ) 2( ) → 2( ) 2( ) cos x sen x cos x sen x 2( ) 2( ) 2( ) 2( ) sen x + cos x = 12( ) 2( ) (verdadeiro) (verdadeiro)
Compartilhar