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Question
Without using trigonometric identity , show that :
`sec70^circ sin20^circ - cos20^circ cosec70^circ = 0`
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Solution
`sec70^circ sin20^circ - cos20^circ cosec70^circ = 0`
Consider `sec70^circ sin20^circ - cos20^circ cosec70^circ`
⇒ `sec(90^circ - 20^circ)sin20^circ - cos20^circ . cosec(90^circ - 20^circ)`
⇒ `cosec20^circ sin20^circ - cos20^circ sec20^circ`
⇒ `1/sin20^circ . sin20^circ - cos20^circ . 1/cos20^circ`
⇒ 1 - 1 = 0
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