Find the value of sin 30° geometrically.  from Mathematics In

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 Multiple Choice QuestionsShort Answer Type

111. Express the following in terms of trigonometric ratios of angles lying between 0° and 45°
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114. Express the following in terms of trigonometric ratios of angles lying between 0° and 45°
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 Multiple Choice QuestionsLong Answer Type

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#6 {main}</pre> find the value of sinA. cosB + cosA. sinB
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116. If ∠ZB and ∠Q are acute angles such that sin B = sin Q, then prove that ∠B = ∠Q.
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 Multiple Choice QuestionsShort Answer Type

117. In ΔABC right angled at A, given ∠B = 30°, AC = 3 cm. Find AB, BC and ∠ACB.
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118. Find the value of sin 30° geometrically. 


Consider an equilateral ΔABC.
Since each angle in a equilateral A is 60°.
∴ ∠A = ∠B = ∠C = 60°
Draw a perpendicular from A on side BC.
Now, ΔABD= ΔACD => BD = DC
and ΔBAD = ΔCAD [C.P.C.T.]

Consider an equilateral ΔABC.Since each angle in a equilateral A is
Let AB = 2a. Then, BD space equals space 1 half BC space equals space straight a
In right ΔADB, by Pythagoras theorem.
AD squared plus BD squared space equals space AB squared space space rightwards double arrow space space AD squared space equals space AB squared minus BD squared space equals space left parenthesis 2 straight a right parenthesis squared minus straight a squared space equals 3 straight a squared space
rightwards double arrow space space space AD squared space equals space 3 straight a squared space rightwards double arrow space space AD space equals space straight a square root of 3
Now, in right ΔADB,
sin space 30 degree space equals space BD over AB equals fraction numerator straight a over denominator 2 straight a end fraction equals 1 half.

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119. Find the value of tan 60°, geometrically.
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120.

If sin thin space left parenthesis straight A minus straight B right parenthesis space equals space 1 half comma space space space space space cos space left parenthesis straight A plus straight B right parenthesis space equals space 1 half comma space space space 0 degree less than straight A plus straight B less or equal than 90 degree comma space space straight A greater than straight B. Find A and B.

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