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kenneyfamily
 3 years ago
if cos A= 0.8 and 270 < A < 360, find the exact value of sin2A
a)0.28
b)0.96
c)0.96
d)0.6
kenneyfamily
 3 years ago
if cos A= 0.8 and 270 < A < 360, find the exact value of sin2A a)0.28 b)0.96 c)0.96 d)0.6

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jim_thompson5910
 3 years ago
Best ResponseYou've already chosen the best response.1Hint: sin(2A) = 2*sin(A)*cos(A) So you need to find the sin(A) first using the value of cos(A)

kenneyfamily
 3 years ago
Best ResponseYou've already chosen the best response.1hmm how would i do that ?

jim_thompson5910
 3 years ago
Best ResponseYou've already chosen the best response.1Using the idea cos^2 + sin^2 = 1

jim_thompson5910
 3 years ago
Best ResponseYou've already chosen the best response.1but it's negative because we're in quadrant IV (sine is negative here)

jim_thompson5910
 3 years ago
Best ResponseYou've already chosen the best response.1so sin(A) = 0.6

jim_thompson5910
 3 years ago
Best ResponseYou've already chosen the best response.1now use sin(2A) = 2*sin(A)*cos(A)
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