MYTUTOR SUBJECT ANSWERS

699 views

How can I remember trig identities?

Trigonometric identities are sometimes tricky, as they are very hard to distinguish one from another. The best way of doing it is obviously by practising, but one thing I always find helpful is to give an example. In the case of cos(a+b), we expand it as cos(a) * cos(b) - sin(a) * sin(b). How can I check that I am sure? Well, if b = 0, then the right hand side term becomes cos(a)*1-sin(a)*0 = cos(a) = cos(a+0). Checked. Is cos(-a-b) = cos(a+b)? Yes, it is. cos(-a)*cos(-b) = cos(a) * cos(b), as cos is an even function and sin(-a)*sin(-b) = -sin(a)*(-sin(b)) = sin(a)*sin(b), as sin is odd. Hence the identity is unchanged.

So, we have taken to important properties of trigonometric functions which are still available on our guessed identity, thus we strongly believe is true, which it is.

Marius S. A Level Maths tutor, GCSE Maths tutor

2 years ago

Answered by Marius, who tutored A Level Maths with MyTutor


Still stuck? Get one-to-one help from a personally interviewed subject specialist

324 SUBJECT SPECIALISTS

£20 /hr

Giorgos A.

Degree: Mechanical Engineering with Renewable Energy (Masters) - Edinburgh University

Subjects offered:Maths, Physics

Maths
Physics

“Feel rewarded helping younger students. Nobody is born knowing everything, life is a learning process and my aim is to help you achieve your goals.”

Trusted by schools

|  5 completed tutorials

PremiumTimothy N. A Level Design & Technology tutor, GCSE Design & Technolog...
£36 /hr

Timothy N.

Degree: Architecture and Environmental Engineering (Masters) - Nottingham University

Subjects offered:Maths, Physics+ 2 more

Maths
Physics
Design & Technology
-Personal Statements-

“Hi there, I have a passion for helping students achieve, and believe that with my 200+ hours of experience, we will be able to surpass the grades you want!”

£26 /hr

Scott R.

Degree: PGCE Secondary Mathematics (Other) - Leeds University

Subjects offered:Maths, Further Mathematics

Maths
Further Mathematics

“I am currently completing 2 PGCEs in Leeds. I have always had a passion for maths and my objective is to help as many as possible reach their full potential.”

About the author

£20 /hr

Marius S.

Degree: Applied Mathematics (Bachelors) - Edinburgh University

Subjects offered:Maths

Maths

“Top tutor from the renowned Russell university group, ready to help you improve your grades.”

MyTutor guarantee

You may also like...

Other A Level Maths questions

Why does d/dx (tan(x)) = sec^2(x)?

Where z is a complex number, what is the cartesian form of |Z-2+3i| = 1?

Differentiate with respect to X: x^2 + 2y^2+ 2xy = 2

Solve for 0<=θ<π, the equation sin3θ-(sqrt3)cosθ=0 (C2)

View A Level Maths tutors

We use cookies to improve your site experience. By continuing to use this website, we'll assume that you're OK with this. Dismiss

mtw:mercury1:status:ok