Tanpa kalkulator atau tabel, hitunglah nilai dari :
a. sin 15o

Jawab :
sin 75o = sin (45 + 30)o
= sin 45o.cos 30o + cos 45o sin 30o
= 1/2 √2 . 1/2 √3 + 1/2 √2 . 1/2
= 1/2 √6 + 1/4 √2
= 1/2 (√(6 ) + √2 )
a. tan 15o = tan (45o – 30o)
= (tan 45° - tan 30°)/(1 +tan 45° tan 30°)
= (1 - 1/(3 ) √3)/(1+1 1/3 √3)=((3-√3)/3)/((3 + √3)/3)
= (3- √3)/(3+ √3) ˟ (3- √3)/(3- √3)
= (9-6√3+3)/(9-3)
= 2 - √3

Jawabanmu

2014-04-17T14:46:17+07:00
nilai tangen 300 derajat ?
jawab:
tan 300 = -cot (270 + 30)
               -cot 30
               -  \sqrt{3}
2014-04-17T18:23:40+07:00
Hitung lah nilai dari (tg 60) ² + 4 (sin 60)² = ....... ?

jawab :

(tg 60)² + 4 (sin 60 )²  =
= (√3)²  + 4 (1/2 × √3)²
= 3  +  4 . 3/4
= 3 + 3
= 6