Question

Sabiendo que tg 5x • ctg (x +40) =1, calcula cos 3x

Answer 1

tg 5x • ctg (x +40) =1

tg 5x = 1/ctg (x +40)

tg 5x = tg(x+40)

5x = x+40

4x = 40

x = 10

piden calcular cos 3x

reemplazando

cos 30

√3/2