Solve this : Please don't send any links please 25 (a) Without using trigonometrical tables, evaluate72 - Maths - Introduction to Trigonometry

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Solve this : Please don't send any links
please

25   ( a )   Without   using   trigonometrical
  tables ,   evaluate 7 2 cos   70 ° sin  
20 ° + 3 2 × cos   55 °   cosec   35
° tan   5 °   tan   25 °   tan
  45 °   tan   85 °   tan   65
°

Neha Sethi · Accepted Answer

Dear student
We have,72×cos70°sin20°+32×cos55 °×cosec35°tan5° tan25° tan45° tan85° tan65°=72×cos90°-20°sin20°+32×cos55°× cosec90°-55°tan90°-85° tan90°-65°×1×tan85°×tan65°=72×sin20°sin20°+32×cos55 °×sec55°cot85°× cot65°×1×tan85°×tan65°=72+32×cos55° ×1cos55°1tan85°×1tan65°×1×tan85°×tan65°=72+32=5Note:tanx=1cotxsecx=1cosxcos90°-x=sinxcot90°-x=tanxcosec90°-x=secxsin90°-x=cosxtan90°-x=cotx
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Solve this : Please don't send any links please . 25 . ( a ) Without using trigonometrical tables , evaluate 7 2 . cos 70 ° sin 20 ° + 3 2 × cos 55 ° cosec 35 ° tan 5 ° tan 25 ° tan 45 ° tan 85 ° tan 65 °

Solve this : Please don't send any links please .

$25 . (a) Without using trigonometrical tables, evaluate \frac{7}{2} . \frac{\cos 70 °}{\sin 20 °} + \frac{3}{2} \times \frac{\cos 55 ° cosec 35 °}{\tan 5 ° \tan 25 ° \tan 45 ° \tan 85 ° \tan 65 °}$