90° – 60° = 30° ———– (1) From the trigonometry formula, sin (90° – a) = cos a We can write, Sin (90° – 30°) = cos 30° Sin 60° = cos 30° —— (2) We know that the value of sin 60 degrees is √3/2 Now substitute the value in (2) √3/2 = cos 30° Therefore, the value of cos 30 degrees is √3/2 Cos 30° =√3/2