Answer:
3rd option
Step-by-step explanation:
Using the identity
sin²x + cos²x = 1 ( subtract sin²x from both sides )
cos²x = 1 - sin²x ( take the square root of both sides )
cosx = ± [tex]\sqrt{1-sin^2x}[/tex]
Given
sinθ = [tex]\frac{21}{29}[/tex] and 0 < θ < 90 , then
cosθ
= [tex]\sqrt{1-(\frac{21}{29})^2 }[/tex]
= [tex]\sqrt{1-\frac{441}{841} }[/tex]
= [tex]\sqrt{\frac{400}{841} }[/tex] = [tex]\frac{\sqrt{400} }{841}[/tex] = [tex]\frac{20}{29}[/tex]
