Question

cho sina+cosa=1 tính \(sin^3a+cos^3a\)

Answer 1

\(sinacosa=\dfrac{\left(sina+cosa\right)^2-1}{2}=\dfrac{1-1}{2}=0\)

\(sin^3a+cos^3a=\left(sina+cosa\right)^3-3cosa\cdot sina\left(sina+cosa\right)=1\)

Answer 2

\(sinacosa=\dfrac{\left(sina+cosa\right)^2-1}{2}=\dfrac{1-1}{2}=0\)

\(sin^3a+cos^3a=\left(sina+cosa\right)^3-3cosa.sina\)\(\left(sina+sosa\right)=1\)