Q11 of 43 Page 1

Prove the following:

Let, sin-1 = x & cot-1 = y


sin x = & cot y =


As, sin x = 3/5 tan x = 3/4 {using basic t-ratios}


And cot y = 3/2 tan y = 2/3


tan-1(3/4) = x & tan-1(2/3) = y


sin-1 + cot-1 = tan-1 + tan-1


sin-1 + cot-1 = { tan-1x + tan-1y = tan-1


sin-1 + cot-1 = …eq(1)


LHS = cos (sin-1 + cot-1)


LHS = cos () {from equation 1}


Let, = z (say)


LHS = cos z


Now we need to find the value of cos z to prove the given equation



{using basic t-ratios}


Using the LHS from the given equation,


LHS = RHS


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