Question

[Thạch Trần Hoàng]

tính giá trị biểu thức sau:

C = ( tan²10^o / cot²80^o ) + ( tan²20^o : cot²70^o ) + ... + ( tan²40^o : cot²50^o ) + tan²45^o

Answer 1

[Nguyễn Việt Lâm]

\(C=\frac{tan^210}{tan^2\left(90-80\right)}+\frac{tan^220}{tan^2\left(90-70\right)}+...+\frac{tan^240}{tan^2\left(90-50\right)}+tan^245\)

\(=\frac{tan^210}{tan^210}+\frac{tan^220}{tan^220}+\frac{tan^230}{tan^230}+\frac{tan^240}{tan^240}+1\)

\(=1+1+1+1+1=5\)