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Question : 23 of 160
Marks:
+1,
-0
Solution:
‌‌| cos‌15∘‌cos2‌22‌−sin‌75∘sin‌252 |
| cos215∘−cos275∘ |
‌=‌| cos‌15∘(cos222−sin‌252) |
| cos215∘−sin‌215∘ |
(| ∵sin‌75∘=sin‌(90∘−15∘) |
| =cos‌15∘ |
)‌=‌| cos‌15∘(−) |
| cos‌30∘ |
‌=‌‌| [cos‌45∘+cos(90+15∘)] |
|
‌=‌(cos‌15∘‌cos‌45∘−sin‌15∘‌cos‌15∘)‌=‌(2‌cos‌15∘‌cos‌45∘−2‌cos‌15∘‌s‌i‌n‌15∘)‌=‌[cos(60∘)+cos‌30∘−sin‌30∘]‌=‌(‌)=‌
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