Question

sec70.sin20-cos20.cosec70

Answer 1

sec70 * sin20 - cos20 * cosec70 

[sec(90-20) * sin20 ] - [ cos(90-70) * cosec70]

[cosec20 * sin20] - [sin70 * cosec70] 
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Now, 

cosec20 * sin20 = 1/sin20 * sin20 = 1
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sin70 * cosec70 = 1/cosec70 * cosec70 
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Then,

1-1

= 0



 i hope this this will help you


-by ABHAY

Answer 2

Answer: The answer is 0.

Step-by-step explanation:

Here, the given expression is,

$sec 70^{\circ}.sin 20^{\circ}-cos 20^{\circ} .cosec 70^{\circ}$

$=\frac{sin 20^{\circ}}{cos 70^{\circ}} - \frac{cos 20^{\circ}}{sin 70^{\circ} }$

( Because sec x = 1/cos x and cosec x = 1/sin x)

$=\frac{sin 20^{\circ}}{cos (90-20)^{\circ}} - \frac{cos 20^{\circ}}{sin (90-20)^{\circ} }$

$=\frac{sin 20^{\circ}}{sin 20^{\circ}} - \frac{cos 20^{\circ}}{cos 20^{\circ} }$

( Because, sin(90-x) = cos x and cos(0-x) = sin x )

$=1-1=0$

Hence,

$sec 70^{\circ}.sin 20^{\circ}-cos 20^{\circ} .cosec 70^{\circ}=0$