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Question : 22 of 160
Marks:
+1,
-0
Solution:
Consider the expression,
cos25∘−cos215∘−sin215∘+sin235∘+cos215∘sin15∘−cos5∘sin35∘ =cos5∘(cos5∘−sin35∘)−cos15∘(cos15∘−sin15∘)+sin235∘−sin215∘ =cos5∘(cos5∘−cos55∘)−cos15∘(cos15∘−cos75∘)+sin250∘sin220∘ =cos5∘(2sin30∘sin25∘)−cos15∘(2sin45∘sin30∘)+sin50∘sin20∘ =(| −+cos5∘sin25∘ |
| +sin50∘sin20∘ |
). =(−+(2cos5∘cos65∘)+(2sin50∘sin20∘)) =−+[2cos45∘cos15∘] =−+ =0
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