Question

Wiedząc, że jest kątem ostrym i , oblicz wartość wyrażenia: .

Answer 1

tg alfa = y/x = 3

zatem   y = 3  oraz  x = 1

wtedy  r^2 = x^2 + y^2 = 1 + 3^2 =1 + 9 = 10

r = p(10)

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sin alfa = y/r = 3/p(10)

cos alfa = x/r = 1/ p(10)

Mamy więc

8 cos alfa = 8 /p(10)

7 sin alfa = 21/ p(10)

5 cos alfa = 5 /p(10)

2 sin alfa = 6 / p(10)

W = [ 8 / p(10)  - 21/ p(10)]*[ 5/ p(10) + 6/ p(10)] =

= [- 13/p(10)] * [ 11/ p(10)] = - 143/10 = -14,3

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