mathemerize

What is the Value of Sin 54 Degrees ?

Solution : The value of sin 54 degrees is \(\sqrt{5} + 1\over 4\). Proof : We know that value of cos 36 degrees is \(\sqrt{5} + 1\over 4\). Since 54 degree is the complement of 36 degree. \(\therefore\) sin 54 = sin(90 โ€“ 36) = cos 36 = \(\sqrt{5} + 1\over 4\) Hence, sin 54 โ€ฆ

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What is the Value of Sin 72 Degrees ?

Solution : The value of sin 72 degrees is \(\sqrt{10 + 2\sqrt{5}}\over 4\). Proof : We know that value of cos 18 degrees is \(\sqrt{10 + 2\sqrt{5}}\over 4\). Since 72 degree is the complement of 18 degree. \(\therefore\) sin 72 = sin(90 โ€“ 18) = cos 18 = \(\sqrt{10 + 2\sqrt{5}}\over 4\) Hence, sin 72 โ€ฆ

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What is the Value of Cos 18 Degrees ?

Solution : The value of cos 18 degrees is \(\sqrt{10 + 2\sqrt{5}}\over 4\). Proof : We know that the value of sin 18 degrees is \(\sqrt{5} โ€“ 1\over 4\). Putting \(\theta\) = 18 inย  \(cos \theta\) = \(\sqrt{1 โ€“ sin^2 \theta}\), we get cos 18 = \(\sqrt{1 โ€“ sin^2 18}\) = \(\sqrt{1 โ€“ ({\sqrt{5} โ€“ โ€ฆ

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What is the Value of Sin 18 Degrees ?

Solution : The value of sin 18 degrees is \(\sqrt{5} โ€“ 1\over 4\). Proof :ย  Let \(\theta\) = 18 degrees. Then, \(5\theta\) = 90 degrees \(\implies\)ย  ย \(2\theta\) + \(3\theta\) = 90 \(\implies\)ย  ย \(2\theta\) = 90 โ€“ \(3\theta\) \(\implies\)ย  ย \(sin 2\theta\) = \(sin (90 โ€“ 3\theta)\) \(\implies\)ย  \(sin 2\theta\) = \(cos 3\theta\) By using the formula โ€ฆ

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Prove that cot A + cot (60 + A) โ€“ย  cot (60 โ€“ A) = 3 cot 3A.

Solution : We have, L.H.S = cot A + cot (60 + A) โ€“ย  cot (60 โ€“ A) \(\implies\) L.H.S = \(1\over tan A\) + \(1\over tan (60 + A)\) โ€“ \(1\over tan (60 โ€“ A)\) \(\implies\) L.H.S = \(1\over tan A\)+ \(1 โ€“ \sqrt{3} tan A\over \sqrt{3} + tan A\) โ€“ \(1 + \sqrt{3} โ€ฆ

Prove that cot A + cot (60 + A) โ€“ย  cot (60 โ€“ A) = 3 cot 3A. Read More ยป

Prove that tan A + tan (60 + A) โ€“ย  tan (60 โ€“ A) = 3 tan 3A.

Solution : We have, L.H.S = tan A + tan (60 + A) โ€“ย  tan (60 โ€“ A) \(\implies\) L.H.S = tan A + \(\sqrt{3} + tan A\over 1 โ€“ \sqrt{3} tan A\) โ€“ \(\sqrt{3} โ€“ tan A\over 1 + \sqrt{3} tan A\) [ By using this formula, tan (A + B) = \(tan A โ€ฆ

Prove that tan A + tan (60 + A) โ€“ย  tan (60 โ€“ A) = 3 tan 3A. Read More ยป

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