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Appendix
Page 817
An Abbreviated Table of
Trigonometric Identities
1. sin(a ; b) = sinacosb ; cosasinb
2. cos(a ; b) = cosacosb < sinasinb
3. sina + sinb = 2 sin
a + b
a - b
cos
2
2
4. sina - sinb = 2 cos a
a + b
a - b
b sin a
b
2
2
5. cosa + cosb = 2 cos a
a + b
a - b
b cos a
b
2
2
6. cosa - cosb = - 2 sin a
a + b
a - b
b sin a
b
2
2
7. 2 sina sinb = cos(a - b) - cos(a + b)
8. 2 cosa cosb = cos(a - b) + cos(a + b)
9. 2 sina cosb = sin(a + b) + sin(a - b)
10. sin2a = 2 sina cosa
11. cos2a = 2 cos2a - 1 = 1 - 2 sin2a
12. cos2a =
1
1
+ cos2a
2
2
13. sin2a =
1
1
- cos2a
2
2
14. tan(a ; b) =
15. tan2a =
tana ; tanb
1 < tana tanb
2 tana
1 - tan2a
817
Electric Circuits, Eighth Edition, by James A. Nilsson and Susan A. Riedel.
ISBN-13: 978-0-13-198922-1. © 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited reproduction, storage
in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or likewise.
89251_24_AppF
4/4/07
1:13 PM
Page 818
Electric Circuits, Eighth Edition, by James A. Nilsson and Susan A. Riedel.
ISBN-13: 978-0-13-198922-1. © 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited reproduction, storage
in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or likewise.