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Find the exact value of the expression by using appropriate identities. Do not use a calculator.
(tan 77 + tan 43)/(1 - tan 77.tan 43)

2 Answers

4 votes

Answer:

Explanation:

Remember from Trig. identity:

Tan(a + b) = (tan a + tan b)/1 - tana × tan b

From the above,

(tan 77 + tan 43)/1 - tan 77 × tan 43

Comparing Both equations on the LHS,

a = 77

b = 43

Therefore, on the right hand side;

Tan (a + b) = tan (77 + 43)

= tan 120

Tan θ = sin θ/cos θ

Sin 120 = (root3)/2

Cos 120 = -1/2

Therefore, tan 120 = (root3)/2 × -2/1

= -(root3)

User Sybio
by
8.3k points
4 votes

Answer:


-√(3)

Explanation:

From Trigonometric Identity


Tan (A+B)=(tan A + tan B)/(I-tan A\cdot tan B)

Therefore comparing
(tan 77 + tan 43)/(I-tan 77\cdot tan 43) with the above:

A=77, B=43


(tan 77 + tan 43)/(I-tan 77\cdot tan 43)=Tan (77+43)

=Tan 120

Tan is Negative in the Second Quadrant

Tan 120 =
-√(3)

User Zachary Scott
by
7.9k points

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