Show that the equation 2sin^2(x) + 3sin(x) = 2cos(2x) + 3 can be written as 6sin^2(x)+3sin(x) - 5 = 0. Hence solve for 0 < x < 360 degrees. Giving your answers to 1.d.p.

2sin^2(x) + 3sin(x) = 2cos(2x) + 32sin^2(x) + 3sin(x) = 2(cos^2(x) - sin^2(x) ) + 32sin^2(x) + 3sin(x) = 2(1- 2sin^2(x) ) + 32sin^2(x) + 3sin(x) = 2 - 4sin^2(x) + 36sin^2(x) + 3sin(x) - 5 = 0 let sin(x) = yThen solve : 6Y^2 + 3Y - 5 = 0Y = [-3(+ or - ) root(129) ] / 12 = sin(x)sin(x) result always between [-1,1]. As such one of these solutions can be disregarded as it lies outside of this range. Take arcsin of the other result.Gives x = 44.1 degrees. Second solution in the range is 135.9 degrees. Second result calculated from graph or ASTC circle.

TA
Answered by Tom A. Maths tutor

3716 Views

See similar Maths A Level tutors

Related Maths A Level answers

All answers ▸

what does it mean if "b^2 - 4ac < 0" for a quadratic equation (eg y = a*x^2 + b*x + c)


What is the best way to prove trig identities?


The equation 5x sqaured + px + q , where p and q are constants, has roots α and α + 4. (a) Show that p squared = 20q +400.


Solve the differential equation dy/dx = y/x(x + 1) , given that when x = 1, y = 1. Your answer should express y explicitly in terms of x.


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

MyTutor is part of the IXL family of brands:

© 2025 by IXL Learning