Answers

2015-08-18T14:27:51+05:30
Cosec10 - 4sin70
= (1/sin10) - [4 sin (90-20)]
=(1/sin10) - (4 cos 20)
= (1/sin10)(1 - 4cos20sin10)

= (1/sin10)[1 - 2(2cos20sin10)]
= (1/sin10)[1 - 2(sin30 - sin10)]
= (1/sin10)[1 - 2(1/2 - sin10)]
= (1/sin10)[1 - 1 + 2sin10]
= (1/sin10)[2sin10]
= 2  Ans.
1 5 1