Question Number 7996 by ridwan balatif last updated on 27/Sep/16
$${how}\:{to}\:{prove}\:{this} \\ $$$$\frac{\mathrm{1}}{{cos}^{\mathrm{2}} \mathrm{10}^{{o}} }+\frac{\mathrm{1}}{{sin}^{\mathrm{2}} \mathrm{20}^{{o}} }+\frac{\mathrm{1}}{{cos}^{\mathrm{2}} \mathrm{40}}=\mathrm{12} \\ $$
Commented by prakash jain last updated on 27/Sep/16
Commented by prakash jain last updated on 27/Sep/16
$$\mathrm{Looks}\:\mathrm{like}\:\mathrm{it}\:\mathrm{is}\:\mathrm{not}\:\mathrm{equal}\:\mathrm{to}\:\mathrm{12}. \\ $$$$\mathrm{See}\:\mathrm{attached}\:\mathrm{screenshot}\:\mathrm{from} \\ $$$$\mathrm{Wolfram}\:\mathrm{alpha}. \\ $$
Answered by prakash jain last updated on 02/Oct/16
$$\mathrm{answer}\:\mathrm{in}\:\mathrm{comments} \\ $$