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If θ is an acute angle and cos θ = 39/89 what is the value of sinθ?
Question

If θ is an acute angle and cos θ = 39/89 what is the value of sinθ?

A.

49/89

B.

79/89

C.

80/89

D.

50/59

Correct option is C

Given: cosθ=3989\cos \theta = \frac{39}{89}​​
Formula Used: sin2θ=1cos2θ\sin^2 \theta = 1 - \cos^2 \theta​​
Solution:
Substituting the value of cosθ\cos \theta ​into the identity:
sin2θ+(3989)2=1\sin^2 \theta + \left(\frac{39}{89}\right)^2 = 1​​
sin2θ+15217921=1\sin^2 \theta + \frac{1521}{7921} = 1​​
sin2θ=115217921\sin^2 \theta = 1 - \frac{1521}{7921}​​
sin2θ=64007921\sin^2 \theta = \frac{6400}{7921} ​  
sinθ=64007921=8089\sin \theta = \sqrt{\frac{6400}{7921}} = \frac{80}{89} ​​​
sinθ=8089.\sin \theta = \frac{80}{89}.​​
Alternate Method:

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