MYTUTOR SUBJECT ANSWERS

528 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

1 year ago

Answered by Marius, who tutored A Level Maths with MyTutor


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

269 SUBJECT SPECIALISTS

£20 /hr

Liam R.

Degree: Economics (Bachelors) - Durham University

Subjects offered:Maths

Maths

“I study Economics at Durham. I have a passion for maths and hope to share this with you! To find out more, click on my profile & book a free 15-minute meeting!”

£20 /hr

George B.

Degree: Physics with Industrial experience (Masters) - Bristol University

Subjects offered:Maths, Physics+ 1 more

Maths
Physics
-Personal Statements-

“I'm a Physics student at the University of Bristol. My passion is Physics and Maths. I love to help people understand what they previously found hard. ”

£20 /hr

Juris B.

Degree: Computer Science (Bachelors) - St. Andrews University

Subjects offered:Maths, Computing

Maths
Computing

“I am a Computer Science at the University of St. Andrews. Before that however, I was a pupil in a school in the North-East of Scotland. With the combined passion and availability of superb teachers - I was given an opportunity to exce...”

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

How do you differentiate parametric equations?

How do you find the gradient of a line at a certain point when f(x) is in the form of a fraction, where both the numerator and denominator are functions of x?

How do I do integration by parts?

The Chain Rule: Differentiate (x^2 + 1)^5/2 with respect to x

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