The exact value of cosec10 - 4sin70 Share with your friends Share 1 Manbar Singh answered this cosec 10 - 4 sin 70=1sin 10 - 4 sin 90-20 as, cosec θ = 1sin θ=1sin 10 - 4 cos 20 as, sin 90-θ = cos θ=1 - 4 cos 20 . sin 10sin 10=1 - 2 . 2 cos 20 . sin 10sin 10=1 - 2sin20+10-sin20-10sin 10 as, 2 cos A . sin B = sinA+B-sin A-B=1 - 2sin 30 - sin 10sin 10=1 - 212-sin 10sin 10=1 - 1 + 2 sin 10sin 10=2 14 View Full Answer Aditya Ranjan answered this Cosec10 - 4sin70 = (1/sin10) - (4cos20) = (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 3
