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Use the double angle formulae and the identity cos(A+B)≡cos(A)cos(B)−sin(A)sin(B) to obtain an expression for cos 3x in terms of cos x only

To answer, you need to know and be able to use your trigonometric formulae including the double angle formulae on data sheet.

1: cos(3x)=cos(2x+x) = cos(2x)cos(x) - sin(2x)sin(x) split the 3...

Answered by Sam H. • Maths tutor

17832 Views

(2x+3)/(x-4) - (2x-8)/(2x+1) = 1 Solve for x

Multiply out the denominator, take care to multiply both sides of the equation:

(2x+3)(2x+1) - (2x-8)(x-4) = (2x+1)(x-4)

Expand the brackets, pay attention the the signs when multiplying, ex...

Answered by Lucy M. • Maths tutor

3471 Views

There are n sweets in a bag, 6 of which are red. The rest of the sweets are blue. Jen removes 1 sweet from the bag. Jen then takes another sweet from the bag. The probability that Hannah takes two red sweets is 1/3. Show that n²-n-90=0.

We know the total number of sweets is n, and that 6 are red. When Jen takes the first sweet, the probability of it being red is [number of red sweets] / [how many there are] = 6/n . For the second sweet, ...

Answered by Amy B. • Maths tutor

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Lewis wins £360 in a prize draw. He gives 15% to charity and puts 3/8 into his savings. The rest he uses to buy a bike. How much of the money has Lewis got left for this bike? Note: do not use a calculator

10% of £360 is £36. Therefore 5% of £360 would be £18 (half of the 10% figure). Added together, 15% of £360 would be £54. 1/8 of £360 is £45 (half £360 three times), therefore 3/8 would be £135 (£45*3). £...

Answered by Lewis B. • Maths tutor

3322 Views