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Find the values of theta between 0^(@) a...

Find the values of `theta` between `0^(@)` and `360^(@)` which satisfy the equations
`cos2theta=(1)/(2)`.

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The correct Answer is:
To solve the equation \( \cos 2\theta = \frac{1}{2} \) for values of \( \theta \) between \( 0^\circ \) and \( 360^\circ \), we will follow these steps: ### Step 1: Identify the general solution for \( \cos x = \frac{1}{2} \) The cosine function equals \( \frac{1}{2} \) at specific angles. We know that: \[ \cos x = \frac{1}{2} \implies x = 60^\circ + 360^\circ n \quad \text{or} \quad x = 300^\circ + 360^\circ n \quad (n \in \mathbb{Z}) \] ### Step 2: Substitute \( 2\theta \) for \( x \) Since we have \( \cos 2\theta = \frac{1}{2} \), we can set: \[ 2\theta = 60^\circ + 360^\circ n \quad \text{or} \quad 2\theta = 300^\circ + 360^\circ n \] ### Step 3: Solve for \( \theta \) Now, we will solve for \( \theta \) in both cases. **Case 1:** \[ 2\theta = 60^\circ \implies \theta = \frac{60^\circ}{2} = 30^\circ \] **Case 2:** \[ 2\theta = 300^\circ \implies \theta = \frac{300^\circ}{2} = 150^\circ \] ### Step 4: Consider additional solutions Since \( n \) can be any integer, we also consider \( n = 1 \) for both cases: **For \( n = 1 \):** - From \( 2\theta = 60^\circ + 360^\circ \cdot 1 \): \[ 2\theta = 420^\circ \implies \theta = \frac{420^\circ}{2} = 210^\circ \] - From \( 2\theta = 300^\circ + 360^\circ \cdot 1 \): \[ 2\theta = 660^\circ \implies \theta = \frac{660^\circ}{2} = 330^\circ \] ### Step 5: Collect all solutions The values of \( \theta \) that satisfy \( \cos 2\theta = \frac{1}{2} \) within the range \( 0^\circ \) to \( 360^\circ \) are: \[ \theta = 30^\circ, 150^\circ, 210^\circ, 330^\circ \] ### Final Answer: The values of \( \theta \) are \( 30^\circ, 150^\circ, 210^\circ, \) and \( 330^\circ \). ---
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ICSE-TRIGONOMETRICAL FUNCTIONS -Exercise 4(d)
  1. Find the values of theta lying between 0^(@) and 360^(@) when tan th...

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  2. Find the values of theta lying between 0^(@) and 360^(@) when sec th...

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  3. Find the values of theta lying between 0^(@) and 360^(@) when sin th...

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  4. Find the values of theta lying between 0^(@) and 360^(@) when tan th...

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  5. Find the values of theta lying between 0^(@) and 360^(@) when sin th...

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  6. Find the values of theta lying between 0^(@) and 360^(@) when costhe...

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  7. If 0^(@)lt theta lt 90^(@) and cos theta=(4)/(5) find the values of ...

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  8. If 0^(@)lt theta lt 90^(@) and cos theta=(4)/(5) find the values of ...

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  9. If 0^(@)lt theta lt 90^(@) and cos theta=(4)/(5) find the values of ...

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  10. If 0^(@)lt theta lt 90^(@) and cos theta=(4)/(5) find the values of ...

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  11. Find six angles for which sin theta=-(sqrt(3))/(2).

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  12. Find all the angles between 0^(@) and 720^(@) whose tangent is -(1)/(s...

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  13. Find the values of theta between 0^(@) and 360^(@) which satisfy the e...

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  14. Find the values of theta between 0^(@) and 360^(@) which satisfy the e...

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  15. If tan theta=0.4, when theta lies between 0^(@) and 360^(@), write dow...

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  16. If cosx^(@)=sin 200^(@), find the possible values of x between -180^(@...

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  17. If A,B,C are angles of a triangle, prove that cosC=-cos(A+B).

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  18. If A,B,C are angles of a triangle, prove that "tan "(B+C)/(2)="cot"...

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  19. If A,B,C are angles of a triangle, prove that (tan (B+C)+tan(C+A)+ta...

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  20. If A,B,C,D are the angles of a quadrilateral, prove that "cos"1/2(A+B)...

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