explain (Question: 326253.0 )

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Shrinam

· started a discussion

· 1 Months ago

explain (Question: 326253.0 )

please give detailed solution

Question:

If $\sin α + s i n β = a$ and $\cos α + \cos β = b$ then cos $(α + β)$ is equal to

Options:

$\frac{b^{2} - a^{2}}{b^{2} + a^{2}}$

$\frac{b^{2} + a^{2}}{{2 b}^{2} + a^{2}}$

$\frac{a^{2} - b^{2}}{b^{2} + a^{2}}$

$\frac{b^{2} + a^{2}}{{2 (b}^{2} + a^{2})}$

Solution:

Ans: (a)

Knowledge Expert

· commented

· 1 Months ago

Dear Student
The solution is already provided in detailed manner
But for more clear clarity we would suggest you to re-revise trigonometric identities and their relations.
In this question you would require following identities
sina*sinb+cosa*cosb=cos(a-b)
cosa*cosb-sina*sinb=cos(a+b)
cos^2a-sin^2a=cos2a
cosa+cosb=2cos(a+b/2)*cos(a-b/2)
You can re-revise more identities for your own good
Keep learning with us
Regards
Team TopRankers

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