Introduction to trigonometry [autosaved]

INTRODUCTION TO TRIGONOMETRY

KOMAL RANAWAT9STDPLM

TRIGONOMETRY

0Trigonometry (from Greek trigōnon, "triangle" and metron, "measure") is a branch of mathematics that studies relationships involving lengths and angles of triangles.

0Right Angled Triangle0We usually know another angle .θ0And we give names to each side:0Adjacent is adjacent (next to) to the angle θ0Opposite is opposite the angle .θ0 the longest side is the Hypotenuse

RIGHT ANGLED TRIANGLE

TRIGONOMETRIC RATIOS

0Sine Function:0 sin( ) = θ Opposite / Hypotenuse0Cosine Function:0 cos( ) = θ Adjacent / Hypotenuse0Tangent Function:0 tan( ) = θ Opposite / Adjacent

Example1: What is the sine of 35°?

0Using this triangle (lengths are only to one decimal place):

0 sin(35°) = Opposite / Hypotenuse = 2.8/4.9 = 0.57...

Q1. In Δ ABC, right-angled at B, AB = 24 cm, BC = 7 cm. Determine(i) SinA , CosA

(ii) SinC , CosC.

0 A. sin A =7/25 , cos A= 24/25, sin C=24/25, cos C=7/250 B. sin A =24/25 , cos A= 7/25, sin C=7/25, cos C=24/250 C. sin A =7/28, cos A= 25/7, sin C=25/24, cos C=25/70 D. sin A =24/28 , cos A= 24/7, sin C=7/26, cos C=25/24

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Q2. In the figure, find tan P – cot R.

0A. tanP-cotP = 10B. tanP-cotP = 20C. tanP-cotP = -10D. tanP-cotP = 0

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Q3. sin A =3/4, calculate cos A and tan A.

0A. cos A = 7/4, tan A = 3/70B. cos A = 4/7, tan A = 7/30C. cos A = tt , tan A =0D. cos A= , tan A =

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What’s the right answer then ?

Q4. Given 15 cot A = 8, find sin A and sec A. Given 15 cot A = 8, find sin A and sec A.

0A. sin A = 15/17 , sec A = 8/170B. sin A =17/8 , sec A = 15/170C. sin A = 15/17 , sec A = 17/80D. sin A =17/15 , sec A = 8/17

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Q5.If tan 2A = cot (A – 18°), where 2A is an acute angle, find the value of A.

0A. 42 degree0B. 36 degree0C. 28 degree0D. 35 degree

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What is the height of the tree on the left ?

0A. 48.80B. 48.70C. 53.60D. 56.3

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Q7. At 57" from the base of a building you need to look up at 55° to see the top of a building. What is the height of the building?

0A. 81.4”0B. 82.4”0C. 83.4”0D. 84.4”

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