Trigonometry! Some of you may have been practicing trigonometry since 8th grade.. But who really likes trigonometry?
Trigonometry is simple logic and once you get the hang of it, it is a very interesting topic in math! And easy, too!
We all know the basics:
sinA = perpendicular/hypotenuse
cosA = base/hypotenuse
tanA = sinA/cosA
cotA = 1/tanA
sinA = 1/cosecA
cosA = 1/secA
tanA = 1/cotA
Here are the important trigonometric identities you’ll need to memorize (YES, MEMORIZE!):
sin2A + cos2A = 1
1 + tan2A = sec2A
To remember this identity, s and t are different letters.
1 + cot 2A = cosec2A
To remember this identity, c (cosec) and c (cot) are the same letters and cot is the inverse of tan.
While solving Proving sums in Trigonometry,
If you get a question like this:
P.T. (1+cosA)/(1 – cosA) = (cosecA + cotA)2
Observe that the RHS has cosecA=1/sinA and cotA=cosA/sinA
Since both cosecA and cotA, when simplified have sinA as the denominator, if we divide EACH TERM on the LHS by sinA, we will solve the sum.
You can also apply the same technique to proving sums which have cosA as the denominator.
Give it a try!
Here’s a link to the PDF file for the above notes:
NOTES – Trigonometric Identities and Tips to Remember
This work by Helpline for ICSE Students (Class X – Class 10) is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
You may print these notes through the PDF file and refer to them as required. We would appreciate it if you abstain from reproducing any part of these notes without our prior permission. For more information, please contact us. Thank you.