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Question : 20 of 160
Marks:
+1,
-0
Solution:
tan‌70°−tan‌20°=a.tan‌50° −= ⇒| sin‌70°.cos‌20°−sin‌20°.cos‌70° |
| cos‌70°‌cos‌20° |
= [∵sin(A−B)=sin‌A‌cos‌B−sin‌B‌cos‌A] ⇒| sin(70°−20°) |
| cos‌70°.cos‌20° |
= ⇒| 2‌sin‌50° |
| 2‌cos‌70.cos‌20° |
= ⇒a{2‌cos‌70°‌cos‌20°}=2‌cos‌50° ⇒a{cos‌90°+cos‌50°}=2‌cos‌50° ⇒a{cos‌50°}=2‌cos‌50° ⇒a=2
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