Question

if sinx=2/3,then find cos 2x​

Answer 1

Solution :

Now, cos2x

= 1 - 2 sin²x

= 1 - 2 (2/3)² [ since sinx = 2/3 ]

= 1 - 2 (4/9)

= 1 - 8/9

= (9 - 8)/9

= 1/9

Rules :

• sin²A + cos²A = 1
• cos²A - sin²A = cos2A
• cos2A = 2 cos²A - 1
• cos2A = 1 - 2 sin²A

Answer 2

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