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A series of trigonometric problems and their solutions involving standard angles. It includes the use of trigonometric functions such as cotangent, secant, sine, cosine, and tangent. The solutions involve the use of trigonometric identities and the trigonometric table for standard angles. The document also includes the verification of trigonometric equations and the evaluation of expressions involving trigonometric functions.
Typology: Exercises
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1. Find the value of each of the following expressions. (i) 4 cot 45 – sec^2 60 + sin^2 60 + cos^2 90 Solution: 4 cot 45 – sec^2 60 + sin^2 60 + cos^2 90 2 = 4 (1) – (2) 2
tan^260 + 4 sin^245 + sec^230 + 5cos^290 cosec(30 ) + sec(60 ) – cot^2 (30 ) 2 2 3 + 4 + + 5(0)^2 Solution: = 2 + 2 – 3 3 + 2 + = = 5 + = =
(iii) 2 4 3 4 15 + 4 19 4 – 3 3 3 3
2. Verify that (i) sin 90 = sin 60 cos 30 + cos 60 sin 30
(ii) cos 0 = cos 2 45 + sin 2 45 Solution: cos 0 = cos 2 45 + sin 2 45 1 = + = + = 1 Verified
3. If = 30 verify that (i) sin 3 = 3 sin – 4 sin^3 Solution: sin 3 = 3 sin – 4 sin^3 L.H.S = sin 3 (30) = sin 90 = 1 R.H.S = 3 sin 30 – 4 sin 3 30 = 3 – 4 = – = – = = 1 Verified. (ii) cos 3 = 4 cos^3 – 3 cos Solution: L.H.S = cos 3 = cos 3 (30) = cos 90 = 0 R.H.S = 4 cos 3 – 3 cos = 4 cos 3 30 – 3 cos 30 = 4 – 3 = 4 – = – = 0
3 3 4 2 2 2 8 3 1 2 2 2 2 3 3 2 2 3 3 3 3 3 3 3 3 3
5. Solve the following equation for 0 < 90 , = 2 Solution: = 2 cos 2 – 3 cos + 2 = 2 sin 2 cos 2 – 3 cos + 2 – 2 sin 2 = 0 cos 2 – 3 cos + 2 (1 – sin 2 ) = 0 cos 2 – 3 cos + 2 cos 2 = 0 3 cos 2 – 3 cos = 0 3 cos (cos – 1) = 0 3 cos = 0 ; cos – 1 = 0 cos = 0 ; cos = 1 = 90 ; = (not possible). 6. When 0 90 , solve the following: (i) 2 cos 3 = 1 Solution: 2 cos 3 = 1 cos 3 = = cos 60
(ii) 2 cos 2 + sin – 2 = 0 Solution: 2 cos 2 + sin – 2 = 0 2(1 – sin^2 + sin – 2 = 0 2 – 2 sin 2 + sin – 2 = 0 2 sin 2 sin = 0 sin (2 sin – 1) = 0 sin = 0 2 sin – 1 = 0 = sin sin = = sin 30
cos 2 3cos + 2 sin 2 cos 2 3cos + 2 sin^2 1 2 60 3 1 2
7. (i) If 4 tan = 5, evaluate Solution: 4 tan = 5
2 – 3 tan 3 + 2 tan = = (ii) If cot = , find the value of. Solution: cot = =
8. Find x from the following equation: tan^2 45 – cos^2 60 = x****. sin 45 cos 45 cot 30 . 2
3 3 x 3 4 2 = x 2cos – 3sin 3cos + 2sin 5 4 2 cos – 3 sin 3 cos + 2sin = =
a cos – sin b cos + sin a b cos – sin cos + sin cot – 1 cot + 1 a b a – b a a + b b
1 x 3 4 2 = 3 3 x 3 4 2