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Trigonometry Review. Unit 3. Identities. RECIPROCAL & QUOTIENT IDENTITIES. r. y. x. PYTHAGOREAN IDENTITIES. r. y. x. cos 2 q = 1 – sin 2 q. cos 2 q + sin 2 q = 1. sin 2 q + cos 2 q = 1. sin 2 q = 1 – cos 2 q. PYTHAGOREAN IDENTITIES. r. y. x.
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Trigonometry Review Unit3 Identities
PYTHAGOREAN IDENTITIES r y x cos2 q= 1 – sin 2q cos2 q+ sin 2q= 1 sin 2q + cos2 q= 1 sin 2q = 1 – cos2 q
PYTHAGOREAN IDENTITIES r y x 1 + tan 2q= sec2q tan 2q= sec2q -1
PYTHAGOREAN IDENTITIES r y x cot2q + 1= cos2 q 1 + cot2q= cos2 q cot2q= cos2 q - 1
2 1 • For the following identities: • Show that it is true for • Prove the result algebraically
2 1 • For the following identities: • Show that it is true for • Prove the result algebraically
SUM AND DIFFERENCE IDENTITIES sin (A + B) ≠ sin A + sin B sin (30o + 60o) ≠ sin 30o + sin 60o sin 90o ≠ sin 30o + sin 60o
SUM AND DIFFERENCE IDENTITIES sin (A + B) = sin A cos B+ sin B cos A sin (30o + 60o) = sin 30o cos 60o + sin 60ocos 30o
This could be shown for each of the sum and difference identities on your data sheet. sin(A + B) = sin A cos B + cos A sin B sin(A – B) = sin A cos B – cos A sin B cos (A + B) = cos A cos B – sin A sin B cos(A – B) = cos A cos B+ sin A sin B
DOUBLE ANGLE IDENTITIES sin(2x) = sin (x) + sin(x) = sin (x) cos (x) + sin (x) cos (x) = 2sin (x) cos (x) sin(A + B) = sin A cos B + sin B cos A
DOUBLE ANGLE IDENTITIES cos(A + B) = cos A cos B – sin B sin B cos (2x) = cos(x)cos (x) – sin(x)sin(x) = cos2 (x) – sin2 (x) cos2 (x) + sin2 (x) = 1 ALSO cos (2x) = 1 – sin2 (x) – sin2 (x) = 1 – 2sin2 (x) cos (2x) = cos2 (x) – (1 – cos2 (x)) = 2cos2(x) – 1
SUM AND DIFFERENCE IDENTITIES sin(x + p) = sin x cos p+ sin pcos x = sin x( – 1 ) + (0)cos x = – sin x sin(A + B) = sin A cos B + sin B cos A
SUM AND DIFFERENCE IDENTITIES sin(A – B) = sin A cos B – sin B cos A = (1)cos x – sin x (0) = cos x
SUM AND DIFFERENCE IDENTITIES cos(A – B) = cos A cos B + sin A sin B cos (x – p/2 ) = cos x cos p/2 + sin x sin p/2 = cos x (0) + sin x (1) = sin x
Simplify cos2x – sin2x – cos (2x) = cos2x – (1 – cos2x) – (2cos2x – 1) = cos2x – 1 + cos2x – 2cos2x + 1) = 0