Question

Làm hộ mình câu e và f với ạ

Answer 1

e/ \(sin^21^o+sin^23^o+...+sin^289^o=\left(sin^21^o+sin^289\right)+...+\left(sin^243+sin^247\right)+sin^245\)

\(=\left(sin^21^o+cos^21^o\right)+...+\left(sin^243^o+cos^243^o\right)+sin^245^o\)

\(=1+...+1+\dfrac{1}{2}=\dfrac{45}{2}\)

Answer 2

f/ \(tan5^o.tan10^o...tan85^o=\left(tan5^o.tan85^o\right).\left(tan10^o.tan80^o\right)...\left(tan40^o.tan50^0\right).tan45^o\)

\(=\left(tan5^o.cot5^o\right).\left(tan10^o.cot10^o\right)...\left(tan40^o.cot40^o\right).tan45^o\)

\(=tan45^o=1\)