RD Sharma - Mathematics

Book: RD Sharma - Mathematics

Chapter: 7. Values of Trigonometric Functions at Sum of Difference of Angles

Subject: - Class 11th

Q. No. 3 of Exercise 7.1

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If cosA = – 24/25 And cosB = 3/5, where π <A < 3π/2 And 3π/2 <B < 2π, find the following:

(i) sin(A +B) (ii) cos(A +B)

Given cosA = -24/25 And cosB = 3/5 where π <A < 3π/2 And 3π/2 <B < 2π

A is in third quadrant And B is in fourth quadrant.

Here, sine function is negative.

We know that


(i) Sin(A +B)

We know that sin(A +B) = sinA cosB + cosA sinB

(ii) Cos(A +B)

We know that cos(A +B) = cosA cosB - sinA sinB

Chapter Exercises

More Exercise Questions


If SinA = 1/2, cosB = , where π/2<A < π And 0 <B < π/2, find the following:

(i) tan(A +B)(ii) tan(A -B)