If cosecA - cotA = q , then show that q 2 -1/q 2 +1 +cosA=0
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Answered by
35
There is a mistake in the question. It should be (q²-1)/(q²+1) -1/cos A = 0
Cosec A - cot A = q
1/q = 1/(cosec A - cot A)
= (cosecA + cotA) / [(cosec A + cotA) (cosec A - cot A)
= (cosec A + cot A )/ 1
q + 1/q = (q²+1) / q = 2 cosec A -- (1)
q - 1/q = (q² - 1) / q = - 2 cot A -- (2)
(2) ÷ (1) =>
(q² -1) / (q² + 1) = - cosec A / cot A
= - sec A
LHS = (q² - 1) / (q² + 1) + 1/cos A
= -sec A + sec A
= 0
Cosec A - cot A = q
1/q = 1/(cosec A - cot A)
= (cosecA + cotA) / [(cosec A + cotA) (cosec A - cot A)
= (cosec A + cot A )/ 1
q + 1/q = (q²+1) / q = 2 cosec A -- (1)
q - 1/q = (q² - 1) / q = - 2 cot A -- (2)
(2) ÷ (1) =>
(q² -1) / (q² + 1) = - cosec A / cot A
= - sec A
LHS = (q² - 1) / (q² + 1) + 1/cos A
= -sec A + sec A
= 0
Anonymous:
best answer
Answered by
15
Step-by-step explanation:
CosecA-CotA= q---(1)
Taking reciprocal,
1/CosecA-CotA=1/q
1(CosecA+CotA)/CosecA-Cot A(CosecA+CotA)=1/q
CosecA+CotA/Cosec^2A-Cot^2A=1/q
CosecA+CotA/1= 1/q {∵Cosec^2A-Cot^2A=1} ---(2)
(1)+(2),
2CosecA=q+(1/q)=q^2+1/q----(3)
(1)-(2),
-2CotA=q-(1/q)=q^2-1/q----(4)
(4)/(3),
-2CotA/2CosecA=q^2-1/q÷q^2+1/q
-CotA/CosecA=q^2-1/q^2+1
(-CosA/SinA)÷(1/SinA)=q^2-1/q^2+1 {∵CotA=CosA/SinA & CosecA=1/SinA}
(-CosA/SinA)(SinA)=q^2-1/q^2+1
-CosA=q^2-1/q^2+1-----(5)
Now, LHS
q^2-1/q^2+1+CosA
⇒ -CosA+CosA=0(from (5) ),RHS.
Hence, proved.
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