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Choose the correct option and justify your choice : sin 2A = 2 sin A is true when A = (A) 0° (B) 30° (C) 45° (D) 60°. Q.2 (3)

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What is the solution of the ncert class 10 chapter introduction of  trigonometry exercise 8.2. I don’t know how to solve the question number 2(3) easily and quickly  . Choose the correct option and justify your choice sin 2A = 2 sin A is true when A = (A) 0° (B) 30° (C) 45° (D) 60°.

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  1. (A) is correct.

    To find the value of A, substitute the degree given in the options one by one

    sin 2A = 2 sin A is true when A = 0°

    As sin 2A = sin 0° = 0

    2 sin A = 2 sin 0° = 2 × 0 = 0

    or,

    Apply the sin 2A formula, to find the degree value

    sin 2A = 2sin A cos A

    ⇒2sin A cos A = 2 sin A

    ⇒ 2cos A = 2 ⇒ cos A = 1

    Now, we have to check, to get the solution as 1, which degree value has to be applied.

    When 0 degree is applied to cos value, i.e., cos 0 =1

    Therefore, ⇒ A = 0°

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