Câu 39

44
tan(a + b) = ((tan a) + (tan b))/(1 - (tan a) (tan b))
tan 60 = √3
tan (20 + 40) = ((tan 20) + (tan 40))/(1 - (tan 20) (tan 40)) = √3
(tan 20) + (tan 40) = √3 (1 - (tan 20) (tan 40))
(tan 20) + (tan 40) = √3 - √3 (tan 20) (tan 40)
(tan 20) + (tan 40) + √3 (tan 20) (tan 40) = √3

Câu 39: Chọn C
(sinα+tanα)^/(cosα +1)^ + 1
= (tanα.cosα+tanα)^/(cosα +1)^ + 1
=tan^α(cosα +1)^/(cosα +1)^ + 1
= tan^α +1
=(sin^α+cos^α)/cos^α
=1/cos^α

Câu 39: Chọn C
(sinα+tanα)^2/(cosα +1)^2 + 1
= (tanα.cosα+tanα)^2/(cosα +1)^2 + 1
=tan^2α(cosα +1)^2/(cosα +1)^2 + 1
= tan^2α +1
=(sin^2α+cos^2α)/cos^2α
=1/cos^2α
Câu 39 trên sai aạ

Câu 42