Show that 2sin(2x)-3cos(2x)-3sin(x)+3=sin(x)(4cos(x)+6sin(x)-3)

When proving trigonometric identites, we must show that the left hand side of the equation = the right hand side. Here we will start with the left hand side (LHS) and show that it is equivalent to the right hand side (RHS).LHS=2sin(2x)-3cos(2x)-3sin(x)+3Using the double angle rules for sin(2x) and cos(2x);LHS=2(2sin(x)cos(x))-3(cos2(x)-sin2(x))-3sin(x)+3Notice that the RHS has sin(x) factorised out, meaning that every term in the LHS has a common factor of sin(x). Currently the LHS has a cos2x term, but we can change this to a sin2x term using the identity: cos2(x)=1-sin2(x) LHS=2(2cos(x)sin(x))-3(1-sin2(x)-sin2(x))-3sin(x)+3=4cos(x)sin(x)-3(1-2sin2(x))-3sin(x)+3=4cos(x)sin(x)-3+6sin2(x)-3sin(x)+3=4cos(x)sin(x)+6sin2(x)-3sin(x)=sin(x)(4cos(x)+6sin(x)-3)=RHSWe have shown that LHS=RHS, therefore the proof is complete.

JB
Answered by Joe B. Maths tutor

15822 Views

See similar Maths A Level tutors

Related Maths A Level answers

All answers ▸

How do you find the angle between two vectors?


The mass, m grams, of a substance is increasing exponentially so that the mass at time t hours is m=250e^(0.021t). Find the time taken for the mass to double in value.


Circle C has equation x^2 + y^2 - 6x + 4y = 12, what is the radius and centre of the circle


A particle of weight 15N is resting on a plane inclined at an angle of 30°. Find : a) the normal force exerted on the particle, b) the coefficient of friction between the particle and the plane, providing it is in limiting equilibrium


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:

© 2026 by IXL Learning