FInd the values in surd form where necessary:
3a) Cos ( 2B + π/6 ) cos (2B -π/6 ) + sin (2B + π/6 ) sin (2B -π/6 )
3b) (Tan 17 + tan 13) / (Tan17 tan 13 - 1 )
The ans for 3a is1/2 and 3b is -1/root3
Maths唔識抵死題(V.QUICK)
2010-10-06 6:55 am
回答 (1)
2010-10-06 7:11 am
✔ 最佳答案
3a)Cos ( 2B + π/6 ) cos (2B -π/6 ) + sin (2B + π/6 ) sin (2B -π/6 )= cos [(2B + π/6) - (2B - π/6)]= cos π/3= 1/23b)(Tan 17 + tan 13) / (Tan17 tan 13 - 1 )= - (tan 17 + tan 13) / (1 - tan17 tan 13 )= - tan(17 + 13)= - tan 30= - 1 / √3or = - √3 / 3
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