Question

find the value of sin2A when cosA=3/5

Answer 1

Hi ,

It is given that ,

cosA = 3/5 ----( 1 )

Sin² A = 1 - cos² A

= 1 - ( 3/5 )²

= 1 - 9/25

= ( 25 - 9 )/25

= 16/25

sinA = √ 16/25

sinA = 4/5 ---( 2 )

Now ,

Sin 2A = 2sinAcosA

= 2 × ( 4/5 ) × ( 3/5 )

= 24/25

Therefore ,

Sin 2A = 24/25

I hope this helps you.

: )

Answer 2

Hii friend,



CosA = 3/5 = B/H


B = 3 , H = 5


By pythagoras theroem,

(H)² = (B)² + (P)²

(5)² = (3)² + (P)²

(P)² = (5)² - (3)²

(P)² = 25 - 9


P² = 16


P = ✓16 = 4


Therefore,


SinA = P/H = 4/5


Sin²A = (4/5)² = 16/25.



HOPE IT WILL HELP YOU....... :-)