Q. Prove that: (2cos2A-1)(2cos2A+1)(2cos4A-1)(2cos8-1)=2cos16A+1

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Solve: tan(theta)+tan2(theta)+root3tan(theta)tan2(theta) = root(3) [ 0 degree <= theta <=360 degree] Soln: ...
Q. Prove that : tan20 + 4sin20 = root 3 Soln: L.H.S. = tan20 + 4sin20 = sin20/cos20 + 4sin20 = (sin20 + 4sin20.cos20)/(cos20) = (sin20 + 2sin40)/cos20 = [sin20 + ...
Q. Prove that: (cos5a.sin2a-cos4a.sin3a)/(sin5a.sin2a-cos4a.cos3a) = cot2a Soln: L.H.S. = (cos5a.sin2a-cos4a.sin3a)/(sin5a.sin2a-cos4a.cos3a) Multiply numerator and denominator by 2. = 2(cos5a.sin2a - ...
Q. Find common difference and first term of an A.S if the sum of the first 6 terms and 9 terms are 183 & 369 respectively. Soln: Here, Sum of the first 6 terms (S6) = 183 Sum of the first 9 terms (S6) = 369 Common difference (d) = ? First T ...
Q. 8cos^3(20) - 8sin^3(10) - 6cos20 + 6sin10 = 2 Soln: L.H.S. = 8cos320 – 8sin310 – 6cos20 + 6sin10 = 2(4cos320 – 4sinn310 – 3cos20 + 3sin10) = 2(4cos320 - 3cos20 + 3sin10 ...