Evaluate the following: `s in 78^0cos 18^0-cos 78^0s in 18^0`

Evaluate the following: sin 78^@ cos 18^@-cos 78^@ sin 18^@

Evaluate the following: sin78^(@)cos18^(@)-cos78^(@)sin18^(0)

Evaluate the following: cos47^(0)cos13^(0)-sin47^(0)sin13^(@)

Find the values of the following: sin75^0 (ii) cos75^0 (iii) sin15^0 (iv) cos15^0

Without using trigonometric tables, evaluate the following: (sec37^0)/(cos e c53^0)+2cot15^0cot25^0cot45^0cot75^0cot65^0(sin^2 18^0+sin^2 72^0)

Evaluate the following limit: (lim)_(x rarr0)(cos x)^(1/s in x)

Evaluate the following limit: (lim)_(x rarr0)(x cos x+2s in x)/(x^(2)+tan x)

Evaluate the following limit: (lim)_(x rarr0)(x cos x-s in x)/(x^(2)+tan x)

Evaluate the following limit: (lim)_(x rarr0)(cos ax-cos bx)/(cos cx-cos dx)

If cos x=tan y,cos y=tan z,cos z=tan x then the value of sin x is (a)2cos18^(0)(b)cos18^(0)(c)sin18^(0)(d)2sin18^(@)