Write cosx - 3sinx in the form Rcos(x + a)

Rcos(x + a) = Rcosxcosa - Rsinxsina
By comparing cosx - 3sinx to the new expression, we can see that:
Rsina = 3 and Rcosa = 1
If we square both and add them, we can see R = √(12+(-3)2) [I would explain why to someone I'm tutoring]
Now that we know R, we can calculate a.
a = arcsin (3/10) [you may want to adjust the value]Then just write into the form...

Answered by Odin G. Maths tutor

8441 Views

See similar Maths A Level tutors

Related Maths A Level answers

All answers ▸

Differentiate y=(3x-1)/(2x-1)


Find the range of values of k for which x²+kx-3k<5 for some x, i.e. the curve y=x²+kx-3k goes below y=5


Differentiate y = x sin(x)


How do we know which formulas we need to learn for the exam?


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences