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Prove that cos 20^(@) cos 40^(@) - sin5^...

Prove that `cos 20^(@) cos 40^(@) - sin5^(@) sin 25^(@) = (sqrt(3)+1)/(4)`.

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Prove that cos20^(@)cos40^(@)-sin5^(@)sin25^(@)=(sqrt(3)+1)/4

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SRISIRI PUBLICATION-IPE SCANNER (TEXUAL BITS)-Very Short Questions (2 marks) (Trigonometric Ratios, Transformations)
  1. Prove that sin50^(@)-sin70^(@)+sin10^(@)=0

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  2. Prove that 4(cos66^(@)+sin84^(@)) = sqrt(3) + sqrt(15).

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  3. Prove that cos 20^(@) cos 40^(@) - sin5^(@) sin 25^(@) = (sqrt(3)+1)/(...

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  4. Prove that cos theta + cos[(2pi)/3 + theta] + cos [(4pi)/(3) + theta] ...

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  5. Prove that cos A + cos((4pi)/3 -A) + cos ((4pi)/3 + A) = 0.

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  6. Find the value of sin 22(1/2)^(@)

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  7. Find the value of sin 75^(@)

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  8. Find the value of tan 75^(@)

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  9. Find the value of tan 75^(@) + cot 75^(@)

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  10. Find the values of cos 22(1/2)^(@) using the value of cos 45°?

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  11. Find the values of tan 22(1/2)^(@)

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  12. Find the values of sin 36^(@)

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  13. Find the value of cos 18^(@)

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  14. If cos A = sqrt((sqrt(2)+1)/(2sqrt(2))), find the value of cos2A

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  15. IF sintheta=4/5 and theta is not in the first quadrant, find the value...

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  16. If cos theta = t(0lt t lt 1) and theta does not lies in the first qua...

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  17. If cos theta = t(0lt t lt 1) and theta does not lies in the first qua...

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  18. If sin A=(12)/(13), cos B= (3)/(5) and neither A nor B is in the first...

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  19. If 0 lt A, B lt 90^(@), cos A= (5)/(13) and sin B =(4)/(5) then find s...

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  20. If sin =(1)/(sqrt10), sin beta =(1)/(sqrt5) and alpha , beta are acu...

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