Question

How to find the value of sec15 without using calculator or table?

Answer 1

Hi,

Explanation:

`sec(15^o)=(1)/(cos(15^o) \\cos((x)/(2) )=\sqrt{(1+cos(x))/(2) } (1st\ quadrant)\\\\cos(15^o)=\sqrt{(1+cos(30^o))/(2) } =\sqrt{(1+(√(3) )/(2) )/(2) }\\\\\\cos(15^o)=\frac{\sqrt{2+√(3)} }{2} \\\\or\\cos(15^o)=(√(2)+√(6) )/(4) \\`