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Prove that `(sin theta + "cosec" theta)^(2)+(cos theta + sec theta)^(2)=(7+ tan^(2) theta + cot^(2) theta).` |
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Answer» We have LHS `= (sin theta + "cosec" theta)^(2)+(cos theta + sec theta)^2 ` ` =(sin^(2)theta + "cosec"^(2)theta +2 sin theta "cosec" theta)+(cos^(2)theta + sec^(2)theta + 2 cos theta sec theta )` ` = (sin^(2) theta + "cosec"^(2)theta +2)+(cos^(2)theta + sec^(2)theta +2) ` ` [ because sin theta "cosec"theta =1 and cos theta sec theta=1] ` ` = (sin^(2)theta + cos^(2)theta)+4+("cosec"^(2) theta + sec^(2) theta)` ` = 1+4+(1+cot^(2) theta)+(1+tan^(2)theta) ` ` [ because sin^(2) theta + cos^(2)theta =1, "cosec"^(2)theta =1+cot^(2) theta and sec^(2)theta=1+tan^(2)theta] ` ` =(7+ tan^(2)theta + cot^(2) theta )= RHS. ` `therefore LHS = RHS. ` |
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