Trigonometric Identities Question 328
Question: Find the value of $ \cot 5{}^\circ \cot 10……..cot85{}^\circ $ .
Options:
A) 1
B) -1
C) 2
D) -2
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Answer:
Correct Answer: A
Solution:
$ cot5{}^\circ cot10{}^\circ ………cot85{}^\circ $ $ =cot5{}^\circ cot10{}^\circ ………cot(90{}^\circ -10{}^\circ )\cot (90{}^\circ -5{}^\circ ) $ $ =cot5{}^\circ cot10{}^\circ ………tan10{}^\circ tan5{}^\circ $ $ =(\tan 5{}^\circ ,\cot 5{}^\circ )(\tan 10{}^\circ \cot 10{}^\circ ) $ ??. $ =(1)(1)(1)…….=1 $
BETA
