CHÚC BẠN HỌC TỐT !!!!!!!!!!!!
Đáp án:
`{3 - 4cos2\alpha + cos4\alpha}/{3 + 4cos2\alpha + cos4\alpha} = tan^4\alpha`
Giải thích các bước giải:
`{3 - 4cos2\alpha + cos4\alpha}/{3 + 4cos2\alpha + cos4\alpha}`
`= {3 - 4cos2\alpha + 2cos^2 2\alpha - 1}/{3 + 4cos2\alpha + 2cos^2 2\alpha - 1}`
`= {2 - 4cos2\alpha + 2cos^2 2\alpha}/{2 + 4cos2\alpha + 2cos^2 2\alpha}`
`= {2(1 - cos2\alpha)^2}/{2(1 + cos2\alpha)^2}`
`= ({1 - 2cos^2\alpha + 1}/{1 + 2cos^2\alpha - 1})^2`
`= [{2(1 - cos^2\alpha)}/{2cos^2\alpha}]^2`
`= ({sin^2\alpha}/{cos^2\alpha})^2`
`= (tan^2\alpha)^2`
`= tan^4\alpha`
