Question

Answer 1

d: \(=sin^220^0+tan50\cdot cot50\cdot cos20\cdot cos20\)

\(=sin^220^0+cos^220^0=1\)

c:

cos 20=sin 70>sin 30

cos50=sin 40<tan40

cos32=sin58<sin60

cot70=tan20>sin20

a: \(cosA=\sqrt{1-\left(\dfrac{3}{5}\right)^2}=\dfrac{4}{5}\)

\(tanA=\dfrac{3}{5}:\dfrac{4}{5}=\dfrac{3}{4}\)

\(cotA=1:\dfrac{3}{4}=\dfrac{4}{3}\)

Answer 2

b) \(sin40^o15'=cos49^o45'\)

    \(sin80^o=cos10^o\)

Sắp xếp theo thứ tự tăng dần: \(cos67^o< cos49^o45'< cos20^o< cos10^o\)