Question

Giúp em câu 2.4b với ạ em cảm ơn

Answer 1

2.4b

(1+tanx + \(\dfrac{1}{cosx}\))(1+tanx - \(\dfrac{1}{cosx}\))

= (1+tanx)² - \(\left(\dfrac{1}{cosx}\right)^2\)

= 1 + 2tanx + tan²x - \(\dfrac{1}{cos^2x}\)

= 2tanx (do 1 + tan²x = \(\dfrac{1}{cos^2x}\))