Question

cho a ≠ kπ/2, k ϵ Z. Chứng minh rằng:
\(\dfrac{1}{2}\sin2a-tan^2a\left(cota-sina.cosa\right)=0\)

Answer 1

Sao ko thấy tham số m nào bạn nhỉ?

Answer 2

\(VT=\dfrac{1}{2}sin2a-tan^2a.cota+\dfrac{1}{2}tan^2a.sin2a\)

\(=\dfrac{1}{2}sin2a\left(1+tan^2a\right)-tana\)

\(=\dfrac{1}{2}sin2a.\dfrac{1}{cos^2a}-tana\)

\(=\dfrac{sina.cosa}{cos^2a}-tana=tana-tana=0\) (đpcm)