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Without using trigonometric tables, prove that :(i) cos -81^@-sin 9^@=0(ii)tan 71^@-cot 19^@=0(iii) cosec 80^@-sec 10^@=0(iv) cosec ^2 72^@-tan^2 18^@=1(v)cos^2 75^@ +cos ^2 15^@=0(vi) tan^2 66^@-cot^2 24^@=0(vii) sin^2 48^@+sin^2 42^@=1(viii)cos^2 57^@-sin^2 33^@=0(ix)(sin 65^@+cos 25^@)(sin 65^@-cos25^@)=0 |
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Answer» Solution :`(IV) LHS =cosec^2 72^@-TAN ^2(90^@-72^@)=cosec^2 72^@-cot ^272=1`. J `(viii) LHS-cos^2 57^@-sin^2 (90^@-57^@)=cos^2 57^@-cos^2 57^@=0`. `(ix) LHS=sin^2 65^@-cos^2 25^@=sin ^2 65^@-cos^2(90-65^@)=sin^2 65^@-sin^2 65^@=0`. |
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