Questions on trigonometry

albert

2009-06-03 6:09 am

Please help me answer these questions:
http://www.flickr.com/photos/81115255@N00/3589330674/
thanks a lot!

更新1:

第三題 tan入面個個係12度

回答 (1)

yuen ki

2009-06-03 6:48 am

✔ 最佳答案

1.. a).tan 45*=h/DB
DB=h -----------------(1)

CD=h/tan 60*------------(2)

b). note that DB=DC+100
DC=DB-100
by (1) DC=h-100 -----(3)
put (3) into (2)
h-100 = h/tan 60*
h tan 60*-100 tan 60* = h
h(tan 60*-1)=tan 60* (100)
h = (100 tan 60*)/(tan 60*-1)
= 236.60

4..LHS=(1/tan^2 Q)- cos ^2 Q
=(cos^2 Q/sin^2 Q) - cos^2 Q
=(cos^2 Q/sin^2 Q) - (cos^2 Q sin^2 Q)/sin^2 Q
=(cos^2 Q(1-sin^2 Q))/sin ^2 Q
=(cos^2 Q cos^2 Q)/sin^2 Q
=(cos^2 Q/sin^2 Q)(cos^2 Q)
=1/tan^2 Q cos ^2 Q
=RHS

2009-06-02 22:50:32 補充：
第二 if 係 = 9/5 就識做 =3=
第三 tan入面個個係12定係12度...係2個唔同既ans=.=

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