Posted by **lindsay** on Tuesday, May 21, 2013 at 5:39am.

Find the exact value of

1. tan 75 degrees

2. Cos 15 degrees

3. Sin 105 degrees

- math -
**Steve**, Tuesday, May 21, 2013 at 11:30am
you know the values for 30 and 45 degrees

use your sum/difference and half-angle formulas

75=45+30

15=30/2

105=90+15

- math -
**hari krishna**, Monday, September 21, 2015 at 12:29am
Tan 75 = tan (45 +30)

= tan 45 + tan 30/1-tan 45 *tan 30

= (1+ 1/√3)/(1-1/√3) = √3 + 1/√3-1

= √3 + 1/√3-1 (afterationalization )

= 2+√3

cos 15 = cos (45 - 30)

= cos 45 cos 30+ sin 45 sin 30

=

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