Commerce (English Medium) Class 11 - CBSE Question Bank Solutions

Prove the following:

`(cos 4x + cos 3x + cos 2x)/(sin 4x + sin 3x + sin 2x) = cot 3x`

Prove the following:

`tan 4x = (4tan x(1 - tan^2 x))/(1 - 6tan^2 x + tan^4 x)`

Prove that: `(cos x  + cos y)^2 + (sin x - sin y )^2 =  4 cos^2  (x + y)/2`

Prove that: `(cos x - cosy)^2 + (sin x - sin y)^2 = 4 sin^2  (x - y)/2`

Prove that: sin x + sin 3x + sin 5x + sin 7x = 4 cos x cos 2x sin 4x

Prove that: `((sin 7x + sin 5x) + (sin 9x + sin 3x))/((cos 7x + cos 5x) + (cos 9x + cos 3x)) = tan 6x`

Prove that: sin 3x + sin 2x – sin x = 4sin x `cos  x/2 cos  (3x)/2`

Find the modulus and the argument of the complex number  `z = – 1 – isqrt3`

Find the modulus and the argument of the complex number `z =- sqrt3 + i`

Convert the given complex number in polar form `sqrt3 + i`

Convert the following in the polar form:

`(1+7i)/(2-i)^2`

Convert the following in the polar form:

`(1+3i)/(1-2i)`