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If cosx = – 3 and p < x < 3π , then the value of sin 2x will be 5 2
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12 25 -
1 15 -
24 25 -
5 26
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Correct Option: C
Here,
cosx = – | and p < x < | |||
5 | 2 |
⇒ x lies in third quadrant, and we know that in third quadrant only tan and cot are positive.
Consider right angled ∆ABC,
Using pythagoras theorem,
AC² = AB² + BC²
⇒ 5² = (–3)² + BC²
16 = BC²
⇒ BC = 4
We know that,
sin2A = 2sinA × cosA
⇒ sin2x = 2 × sinx× cosx
= 2 × | × | ||||
5 | 5 |
= | ||
25 |
∵ Here, sinq is –ve