Posted by lindsay on .
Find the exact value of
1. tan 75 degrees
2. Cos 15 degrees
3. Sin 105 degrees

math 
Steve,
you know the values for 30 and 45 degrees
use your sum/difference and halfangle formulas
75=45+30
15=30/2
105=90+15 
math 
hari krishna,
Tan 75 = tan (45 +30)
= tan 45 + tan 30/1tan 45 *tan 30
= (1+ 1/√3)/(11/√3) = √3 + 1/√31
= √3 + 1/√31 (afterationalization )
= 2+√3
cos 15 = cos (45  30)
= cos 45 cos 30+ sin 45 sin 30
=