how-to-prove-this-1-cos-2-10-o-1-sin-2-20-o-1-cos-2-40-12-

Question Number 7996 by ridwan balatif last updated on 27/Sep/16

h o w t o p r o v e t h i s

\frac{1}{{c o s}^{2} 10^{o}} + \frac{1}{{s i n}^{2} 20^{o}} + \frac{1}{{c o s}^{2} 40} = 12

Commented by prakash jain last updated on 27/Sep/16

Commented by prakash jain last updated on 27/Sep/16

Looks like it is not equal to 12 .

See attached screenshot from

Wolfram alpha .

Answered by prakash jain last updated on 02/Oct/16

answer in comments