Question

if sin A=0.5 what is value of cosA?

Answer 1

Cos A = root(3)/2 = 0.865

Answer 2

Sin A = 0.5 = 1/2

It means for a right angled triangle with angle A
Opposite side = 1
Hypotenuse side = 2

By using Pythagoras theorem
Adjacent side = √(Hypotenuse² - Opposite²)
= √(2² - 1²)
= √3

cos A = Adjacent side / Hypotenuse side
= √3 / 2

∴ cos A = √3 / 2
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ANOTHER METHOD

sin A = 0.5
sin A = sin 30°
A = 30°

Then,
cos A = cos 30 = √3 / 2